He also indicated that the US was preparing a security plan for Kosovo that could supersede the peace accord rejected by the Yugoslav President, Slobodan Milosevic, at the Rambouillet talks.
Appearing at the White House to brief reporters, Mr Clinton was at pains to dispel the impression either that the situation in the Balkans was unforeseen and out of control, or that he was personally cracking under the strain, as some reports had suggested.
He made his carefully staged public appearance after meeting American aid workers, who have recently returned from the Balkans and who supported the official US view that Nato air strikes were not responsible for the forcible mass expulsion of ethnic Albanians from Kosovo. President Clinton has been accused of failing to anticipate the refugee exodus and the resulting humanitarian crisis.
Repeating his warning to President Milosevic that the United States would hold him and his government responsible for the "safety and well being" of the three American servicemen seized on the Macedonia-Kosovo border, Mr Clinton made no direct mention of the Serbian threat to put the men on trial. There were hints, however, that the US was making efforts to avoid such a spectacle. The White House confirmed that messages were being conveyed to the Yugoslav government via Swedish diplomats, who have represented US interests in Belgrade since its diplomats left.
Mr Clinton also set out current US thinking on any post-crisis settlement. "Ultimately we want to make it possible for the victims to return home, to live in security and enjoy self-government," he said.
Intimating a longer-term role for Nato or the US in such an arrangement, he said: "I think there will have to be some sort of security arrangement for them to live safely. And then there will have to be some sort of agreement that entails the autonomy to which they are entitled." He insisted that the peace plan agreed at Rambouillet was still the "framework" for any settlement, but implied that there would have to be military back-up that was stronger than the monitoring arrangements set out before. Any arrangement, he said "will require ... for some period of time some sort of international force that will be able to protect their security".
Many of yesterday's official statements out of Washington were calculated to counter a barrage of political and media criticism of the President and his handling of the crisis.
With the three Americans held captive, a third of Kosovo's population in flight, rumours of an imminent coup in Montenegro, and Macedonia and Albania facing destabilisation by the refugee influx, the White House faced an uphill struggle to preserve its credibility.
Facing the biggest foreign policy crisis of his tenure, Mr Clinton seemed suddenly to have been forsaken by the luck that has been his constant companion during his presidency.
He showed some signs of the heavy cold he has reportedly suffered from this week, but - despite talk that he has been affected by strain and sleepless nights - he appeared calm. In a sign that the administration wanted to reassure its Balkan allies, it was also announced that the Deputy Secretary of State, Strobe Talbott, would visit the region next week.
But there was additional bad news for Mr Clinton in the opinion polls. Two weeks after being hailed as the most competent foreign policy president this century, approval of his handling of foreign policy has slipped from 64 per cent to 54 per cent - and that was before the three US servicemen were taken prisoner.
His decision to order air strikes against Yugoslavia is also proving the least popular of all his recent resorts to military force. Only 53 per cent of those polled approved, compared with 74 per cent who supported air strikes against Baghdad last December, 66 per cent who approved the retaliation against those deemed responsible for the US embassy bombings last August, and the 79 per cent who backed air attacks on Iraq in the Gulf War.
Faced with mounting criticism, Mr Clinton maintained, however, that he still had no intention of authorising the use of ground forces. He had earlier expressed fears about the difficulty of extracting such forces once they had been deployed - a difficulty brought home by the capture of the US servicemen.