Prime Minister David Cameron today called on the United Nations to “ramp up” pressure on the regime of Syrian president Bashar Assad, after international peace envoy Kofi Annan announced he was stepping down.
Mr Cameron said that the resignation of the former UN secretary general showed that the Annan plan, which called for a ceasefire in Syria to pave the way for talks on a political settlement, has not worked.
Speaking in Geneva, Mr Annan cited "finger-pointing and name-calling" in the 15-nation UN Security Council as one of the reasons for his decision to step down.
Russia and China have blocked British-backed resolutions in the Security Council to threaten the Assad regime with global sanctions if it fails to halt the bloodshed in the 17-month uprising.
There was little sign of progress on the issue in Downing Street talks between Mr Cameron and Russian president Vladimir Putin today, after which the two leaders said only that Moscow and London would continue dialogue.
Speaking to Sky News shortly after the announcement of Mr Annan's resignation, Mr Cameron said: "Frankly it shows that the current process isn't working.
"The Annan plan - he has worked very hard at it, but it hasn't worked, because we've got this appalling bloodshed, we've got this slaughter.
"I think what we need to do is actually ramp things up. We need to pass resolutions at the United Nations to put further pressure on Syria. I want to see them under so-called Chapter VII (of the UN Charter), so they have full legal backing of the UN - sanctions, travel bans, asset freezes, all the steps we can take to add to the pressure on the Syrians, and also a very clear warning to them that if they use chemical or biological weapons there will be the most severe consequences to them of all."
Mr Cameron played down the prospect of military intervention by the international community, telling Sky News: "Syria is not Libya. It's a different situation. I don't think military approaches are right in this case. I've thought very carefully about that.
"But I think there's a lot more pressure we can put on and there's a lot we can do, for instance, to help the Syrian opposition with advice and support and I think we can perhaps do more on that.
"We've been giving them non-lethal support, as it were, trying to bring the Syrian opposition together and make them more cohesive. These are all things we can do through the Friends ofSyria group.
"We are very active. We are the ones pushing for further action, we are the ones drafting the UN Security Council resolutions, but tragically they haven't been supported so far by Russia and China - two of the permanent members. We need their backing."
Mr Cameron defended his decision to host Mr Putin for talks at Number 10, at which Syria topped the agenda.
Speaking after the talks, Mr Cameron pointed to differences in the British and Russian approaches to the Syrian crisis.
But he added: "We both want to see an end to that conflict and a stable Syria. We will continue to discuss with our foreign ministers how we can take this forward."
Mr Putin made no direct reference to his country's stance with regard to long-standing ally Damascus, but said that there were areas where Russia and Britain "see eye to eye".
"We agreed to continue working to find a viable solution," said the Russian president.
Mr Cameron later told Sky: "Obviously we don't agree about this, but there is some common ground emerging, I think. The Russians can see that what's happening in Syria is very bad, clearly, for the Syrian people, but I don't think it's in Russia's interest either."
The PM added: "Russia is a member of the Security Council of the UN. We have to speak to them, we need to work with them, we need to work on them to try to get them to move to support transition in Syria, so that we get rid of Assad and we have some sort of change in Syria to stop this appalling bloodshed.
"It's no good just not talking to these people. We have to talk to them and that's what today was about."
Mr Annan was appointed envoy of the UN and the Arab League in February and travelled repeatedly to Syrian capital Damascus in an effort to broker a ceasefire in the uprising, in which 19,000 have died.
His announcement today that he will not seek a renewal of his mandate when it expires on August 31 is a clear sign of acceptance that this approach has failed to deliver the hoped-for breakthrough.
The struggle between regime forces and rebels continued today in Damascus and Syria's largest city Aleppo.
Syrian activists said rebels were using a tank captured from government troops to bombard a military air base in Aleppo. The Bashar regime said it had carried out a string of raids on rebels in neighbourhoods on the south of Damascus, killing and arresting a number of "terrorists".
UN Secretary General Ban Ki-moon said in a statement that he and his Arab League counterpart Nabil Elaraby are in discussions on appointing a successor to Mr Annan.
Mr Ban said Mr Annan deserved "our profound admiration for the selfless way in which he has put his formidable skills and prestige to this most difficult and potentially thankless of assignments".
And Russia's ambassador to the UN Vitaly Churkin said: "We understand that it's his decision. We regret that he chose to do so.
"We have supported very strongly Kofi Annan's efforts. He has another month to go, and I hope this month is going to be used as effectively as possible under these very difficult circumstances."
For Labour, shadow foreign secretary Douglas Alexander said: "Kofi Annan's resignation is the latest sign of the frustration and despair felt by so many in the face of the ongoing failure of the international community to bring an end to the violence in Syria.
"He deserves our gratitude and respect for the way he took on such a difficult and harrowing task with such dignity and determination.
"This latest setback must not be an excuse for inaction, but instead demands a new diplomatic effort to end this conflict which has already gone on too long and cost too many innocent lives.
"If the international community is to live up its responsibility, it must come together now otherwise the conflict will continue long after the battle now raging in Aleppo has ended."