In a rare interview, the Syrian President told the AFP news agency that he realised that the involvement of regional and international forces “means that the solution will take a long time and will incur a heavy price”.
He styled his opponents as “terrorists”, although Syrian forces have mainly been fighting anti-government rebels including the Free Syrian Army, who were initially supported and trained by the US.
Assad told AFP his forces would fight to retake territory “without hesitation”, despite ongoing attempts at a fragile peace process.
He was speaking shortly before diplomats at the current Syria peace talks in Munich agreed a temporary “cessation of hostilities” in Syria's civil war within a week, although efforts to secure a lasting ceasefire fell short.
The deal appeared to be the result of a compromise between the US, which had wanted an immediate stop to fighting, and Russia, which had proposed a ceasefire to start on 1 March.
“The real test is whether or not all the parties honour those commitments and implement them,” John Kerry, the US Secretary of State, said in the early hours of Friday morning.
Discussions between the Syrian regime and anti-government rebels are due to re-start on 25 February after breaking down rapidly last month as Assad’s military made significant advances backed by Russian air strikes.
In recent weeks, government forces have closed in on Aleppo, Syria's largest city, and are now targeting the Free Syrian Army’s last remaining supply line.
Assad’s troops are also moving towards the north-eastern city of Idlib, which is held by Jaysh al-Fatah (Army of Conquest), the Islamist coalition including the al-Qaeda linked Jabhat al-Nusra, Ahrar ash-Sham and Jund al-Aqsa.
They are internationally recognised as terrorist groups and have not been invited to peace talks, but the US-led alliance has been at loggerheads with Syria, Russia and Iran over the inclusion of "moderate" rebels.
Russia’s air strikes, which started in September at Assad’s request, have been accused of “indiscriminately” targeting residential areas and killing countless civilians, while the US-led coalition’s bombing has concentrated on Isis territory.
The West considers Assad’s resignation as the key and perhaps only way to stop the Syrian war, but he has doggedly refused to go.
David Cameron has repeatedly said the Syrian President has no place in the country’s future and has called for peaceful transition to a new government, in line with Barack Obama, Francois Hollande and other leaders in the US-led international coalition.
In pictures: Syria conflict
In pictures: Syria conflict
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Syrians carry children amid debris following a air strike by government forces in the northern city of Aleppo
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A Syrian man carries a girl on a street covered with dust following a air strike by government forces in the northern city of Aleppo
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Syrians react as they stand amid debris following a air strike by government forces in the northern city of Aleppo
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A Syrian man carries a girl amid debris following a air strike by government forces in the northern city of Aleppo
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An injured Syrian man walks out from the rubble of a destroyed building following a air strike by government forces in the northern city of Aleppo
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A Syrian woman makes her way through debris following a air strike by government forces in the northern city of Aleppo
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People stand on the rubble of collapsed buildings at a site hit by what activists said was a barrel bomb dropped by forces loyal to Syria's President Bashar al-Assad, in the Al-Fardous neighbourhood of Aleppo
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Syrian residents stand amid the rubble of destroyed buildings
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A Syrian resident grasps a mattress amid rubble in the al-Firdous neighborhood of the northern city of Aleppo
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A bullet-riddled parking sign stands amid debris in a deserted street leading into the old city of Homs
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A general view shows abandoned buildings on a deserted square in the old city of Homs after Syrian government forces regained control of rebel-controlled areas
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A mosque is pictured through shattered glass in the old city of Homs, as rebel fighters withdrew from the city centre in line with a negotiated withdrawal deal with the government after having held out under tight siege for nearly two years
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Buses carrying Free Syrian Army fighters leaving Homs. Exhausted and worn out from a year-long siege, hundreds of Syrian rebels left their last remaining bastions in the heart of the central city of Homs under a cease-fire deal with government forces. The exit of some 1,200 fighters and civilians will mark a de facto end of the rebellion in the battered city, which was one of the first places to rise up against President Bashar Assad's rule, earning it the nickname of "capital of the revolution"
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Syrian government forces hold up a portrait of President Bashar al-Assad (L) while others raise the national flag on top of a pole in the old city of Homs
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Forces loyal to Syria's President Bashar al-Assad run through Aleppo's Bustan al-Qasr crossing after their release by rebels. They were freed as part of a larger deal which saw the last remaining Syrian rebels in central Homs city evacuate their positions and free captives in several locations in northern Syria
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A Syrian woman and two children walk past heavily damaged buildings in the northern city of Aleppo
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A man carries a wounded girl following a reported bombardment with explosive-packed "barrel bombs" by Syrian government forces in the al-Mowasalat neighborhood of the northern Syrian city of Aleppo
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A wounded man sits as he is treated at a makeshift hospital following a reported bombardment with explosive-packed "barrel bombs" by Syrian government forces in the al-Sakhour district of the northern city of Aleppo
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Debris rises in what Free Syrian Army fighters and Islamic rebels said was an operation to strike Al-Sahaba checkpoint, which is considered a gateway to Al-Dayf valley, and remove forces loyal to Syria's President Bashar Al-Assad in Maarat Al-Nouman, Idlib province
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Men try to put out fire at a site hit by what activists said was an air strike by forces loyal to Syria's President Bashar al-Assad in the town of Azaz, north of Aleppo, near the border with Turkey
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Civil Defence members try to put out fire
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Survivors react at a site hit by what activists said was an air strike by forces loyal to Syria's President Bashar al-Assad in the town of Azaz, north of Aleppo, near the border with Turkey
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Residents queue as they wait to receive food aid distributed by the UNRWA at the Palestinian refugee camp of Yarmouk, south of Damascus
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Belongings of Syrian rebels inside a chapel at Crac des Chevaliers, the world's best preserved medieval Crusader castle in Syria. The village was destroyed in fighting between the government and rebel forces while the castle, listed as a UNESCO world heritage site, also has been damaged over the past two years
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Hosen Sabah, a 16-year-old student is comforted by his mother at a hospital in Damascus. Nosen was wounded by a mortar outside his school, while 14 other students were killed and over 80 wounded
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A Free Syrian Army fighter works on a locally made launcher before firing it towards forces loyal to Syria's President Bashar Al-Assad in Mork town
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Syrian policemen and citizens inspecting the site of a car bomb at the entrance of Moadhamiyet al-Sham neighborhood in rural Damascus. According to Syria's Arab News Agency (SANA), a car bomb explosion has gone off in the countryside of Damascus and initial information say there are casualties, where a car rigged with explosions was remotely detonated at the entrance of Moadhamiyet al-Sham neighborhood in rural Damascus during engineering units it was trying to dismantled it
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Opposition fighters carrying a rocket launcher during clashes against government forces in the Sheikh Lutfi area, west of the airport in the northern Syrian city of Aleppo
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A Syrian man helps a woman to make her way through debris following reported air strikes by government forces in the Halak neighbourhood in northeastern Aleppo
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A Syrian man reacts as he carries the body of injured boy following reported air strikes by government forces in the Halak neighbourhood in northeastern Aleppo. According to the Syrian Observatory for Human Rights, at least 33 civilians were killed in the attack
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Syrian rescue workers carry the body of a woman following reported air strikes by government forces in the Halak neighbourhood in northeastern Aleppo
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Syrians gather at the site of reported air strikes by government forces in the Halak neighbourhood in northeastern Aleppo
Saudi Arabia’s foreign minister reinforced the sentiment today, saying his country’s objective was to remove Assad, which he considers a necessary step to defeat Isis and end the conflict.
The UK almost went to war with the Syrian regime in 2013 after evidence emerged of its use of chemical weapons against civilians, and reports of massacres, war crimes and human rights abuses continue.
The UN hopes to start delivering aid to some besieged areas in Syria within the next 24 hours but around 13.5 million people are in desperate need of food and basic supplies.
More than 250,000 people have been killed and around 11 million displaced in almost five years of fighting in Syria, which partly sparked the European refugee crisis.
Additional reporting by agencies