Mr Cook's speech will be seen as a defence of his support for the British and American bombing of Iraq last month and another signal that the West will soon launch military action against Serbia over its actions in Kosovo.
Some Labour MPs have accused Mr Cook of betraying his roots in the Campaign for Nuclear Disarmament by endorsing Tony Blair's hawkish strategy.
But the Foreign Secretary will declare: "Those of us on the left of centre believe passionately in the rule of law, human rights, democracy and freedom.
"We have a strong tradition for standing up for these values, but we can do so only through a robust approach to the world and a resolve to stand up to those who threaten peace and stability."
Giving the Ernest Bevin Memorial Lecture, commemorating the former trade union leader who became foreign secretary in the postwar Labour government, Mr Cook said: "Bevin was a man of the left ... but he never confused a love of peace with weakness.
"He knew that in a tough world it was not enough just to be right."
The Foreign Secretary said that Bevin understood one important truth - weakness was not a left-wing virtue, and a peaceful and secure world could not be built on a foundation of weakness.
Mr Cook added: "Bevin knew that standing up to dictators, defending freedoms and enforcing the rule of law was a left-wing cause."
The speech came as Mr Blair and his ministers stepped up their preparations for military action in Kosovo after the killing of 45 ethnic Albanians last weekend.
The Prime Minister was due to speak to President Bill Clinton last night and officials from the Contact Group of powers on the Balkans meet in London today. They are Britain, the US, France, Italy, Germany and Russia.
The Prime Minister confirmed in a telephone call to Gerhard Schroder, the German Chancellor, and current holder of the European Union's rotating presidency, that force may have to be used against the Yugoslav President, Slobodan Milosevic.
However, Mr Blair and Mr Schroder also agreed that military action against the backdrop of a political vacuum in Kosovo could prove futile.
Downing Street said there was a "large convergence of views" that President Milosevic's behaviour had been "unacceptable". But the two leaders also agreed that the Kosovo Liberation Army had been "provocative".
In a further sign that military intervention is looming, the crisis in Kosovo dominated yesterday's meeting of the Cabinet in London.
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