Mr Tony Blair cleared the way for air attacks on Serbia "in the next few days", telling MPs: "We have no alternative but to act, and act we will, unless Milosevic even now chooses the path of peace."
But the apparent last-chance offer to President Milosevic came amid mounting evidence that the first NATO strikes were imminent.
And while the British Prime Minister travelled to Berlin for the EU summit, Downing Street made it clear that military action could proceed while he is out of the country.
Mr Blair won general opposition support when he told the Commons: "We must act to save thousands of innocent men, women and children from humanitarian catastrophe, from death, barbarism and ethnic cleansing by a brutal dictatorship; to save the stability of the Balkan region, where we know chaos can engulf the whole of the European Union."
However the Conservative leader, Mr William Hague - while giving Mr Blair "wholehearted support" for the proposed action - made it clear that he would not back the use of ground forces to enforce a deal. And Mr Blair told the SNP leader, Mr Alex Salmond, that he was not planning the use of ground troops.
Mr Hague told Mr Blair that action should have been taken sooner, as opposed to a string of last warnings and ultimatums: "Given the repeated warnings and threats issued over many months, we support taking the action described. Indeed the shadow foreign secretary has often called for similar action."
However, Mr Hague continued: "While we support the use of ground troops to implement a diplomatic settlement, we will not support the use of ground troops to fight for a settlement."
Pressed by Mr Salmond to say if he would use ground troops should the air strikes fail, Mr Blair said: "We support the use of ground troops in supporting the agreement. We do not plan to use ground troops in order to fight our way into Kosovo."
The Prime Minister went on: "It would take a huge commitment, possibly over 100,000 ground troops, which is why we have said that is not our plan."
Anticipating action "in the next few days", Mr Blair said the risks were high both for civilians on the ground and for NATO forces: "But in my judgment the consequences of not acting are more serious still for human life and for peace in the long term."