Senior officials from the six-nation Contact Group on the former Yugoslavia have been meeting in Paris to discuss economic and military options to end the violence.

The European Union and the United States have already banned any new investment in Serbia.

Diplomatic sources said further measures might be announced before being endorsed at a meeting of foreign ministers in London on Friday.

President Clinton also expressed his determination to do all he could to stop the bloodshed in Kosovo, and to prevent it becoming what he called another Bosnia.

He said Washington was working with Britain to get the strongest possible resolution through the United Nations.

Bill Clinton: wants "tough resolution"

Talking to reporters at the White House, Mr Clinton said he would "use all necessary means to try to avoid ethnic cleansing and the loss of human life."

The BBC State Department correspondent says the Clinton administration is indicating that it is prepared to move to a more aggressive approach after relying for months on economic, rather than military pressure, to persuade the Yugoslav leadership to negotiate with Kosovan separatists.

Pressure on the Yugoslav president Slobodan Milosevic also came from Paris, where the French president, Jacques Chirac, said Nato should quickly complete a review of contingency plans, including a possible military intervention.

Yeltsin says no

But the Russian President Boris Yeltsin has warned against any outside military intervention to resolve the conflict in Kosovo.

Speaking in Bonn after talks with German Chancellor Helmut Kohl, Mr Yeltsin said such military intervention would destabilise the Balkans with unpredictable consequences for the whole of Europe.

Ethnic Albanians have demonstrated against the violence in Bonn

The Russian president promised to use his influence with Moscow's traditional ally to help achieve a diplomatic solution.

"I share the concerns of the German people over the situation in Kosovo," Mr Yeltsin told a joint news conference.

"We will meet [with Mr Milosevic] and clarify how we can get out of the situation."

Russia, because of its permanent seat on the United Nations Security Council, could veto any UN resolution allowing the use of force against Yugoslavia.

"Tax for defence"

Meanwhile, there are reports that the self-styled "Kosovo government in exile" , based in Germany, announced it would collect an extra "tax" from an estimated 400,000 Kosovo Albanians living in the West.

Previously the organisation has collected contributions, based on the exiles' earnings, to finance health, educationial and other social programmes in Kosovo.

But the increased "tax" reported on Tuesday was for the "defence of our people" from attacks by Serbian forces, the group, without elaborating further.