If Russia - which wants the United Nations Security Council vote delayed until 26 April - continues to resist, the other three are expected to push for a vote regardless.
The development came after telephone talks between Douglas Hurd, the Foreign Secretary, and his opposite numbers Warren Christopher, the US Secretary of State and Alain Juppe, the French Foreign Minister.,
A Foreign Office spokesman said the decision had been reached in the light of 'the deteriorating situation in Srebrenica, the plight of the people caught up in the fighting and the seriousness of the apparent Serbian determination to ignore the wishes of the international community.'
The three governments plan to talk to the Russians in New York as soon as possible, possibly today, the spokesman said.
Mr Hurd said earlier that an 'international supremo' should be appointed to ensure an embargo was enforced.
Lord Owen, the European Community peace envoy, called for air attacks on the bridges and roads supplying the Serbian forces with oil, ammunition and spare parts, if the fighting did not stop. Despite this call, he refused to accept that his peace plan for Bosnia had collapsed.
The Ministry of Defence said six RAF Tornado F3 fighters will join other Nato aircraft enforcing the no- fly zone over Bosnia. They will be based in Italy. Nato has also asked Turkey to send F-16 fighters, the Turkish Foreign Ministry said. The aircraft - up to 18 in number - will leave over the weekend.
Reginald Bartholomew, President Bill Clinton's special envoy on Bosnia, said earlier in the week that the arms embargo on the Muslims should be lifted if the Serbs did not halt their attacks and agree to the Owen-Vance peace plan. But Lord Owen told the Independent that he still strongly opposed that.
Mr Hurd said the Government had not ruled out air strikes to cut supply lines, but said the option was not being immediately considered. He repeated Britain's opposition to arming the Bosnian Muslims: 'We would be saying to them, 'We have not helped you towards a peaceful settlement so we will leave it to you to fight it out.' '
But Douglas Hogg, Minister of State at the Foreign Office, accepted earlier that Britain would have to consider that option if the Americans came up with a plan.
The US had been delaying a UN Security Council vote to tighten sanctions because President Boris Yeltsin does not want the issue to inflame pro-Serb Russian sentiments while he is facing a crucial referendum on 25 April.
Mr Clinton said yesterday that he was 'distressed' at the situation in Srebrenica: 'We're looking at a number of options. I don't want to rule in or out any, although we've never considered the introduction of American ground forces. . . . I hope the gravity of the situation will develop a consensus among the allies.'
The UN Security Council was in emergency session last night to discuss Srebrenica. It was expected to vote in favour of a resolution declaring that a safe haven for Muslims should be set up in the town.
In London, John Smith, the Labour leader, called for an ultimatum to Bosnian Serb forces that failing an immediate ceasefire the UN would begin air strikes on key lines of supply and communication.
Mr Smith's statement came after calls for tougher action from his own backbenchers, some of whom proclaimed yesterday that 'Margaret Thatcher is right'. Yesterday Baroness Thatcher repeated her call for the West to lift the arms embargo against the Muslims. She has accepted an invitation to visit the Croatian capital, Zagreb, her office said last night.
A Labour Party source said events in Srebrenica were a watershed. If the Serbs did not abide by the Owen- Vance peace plan, air strikes were needed to make sanctions work. 'Action must be punitive if it is to be effective,' Mr Smith said.
In Stockholm, the Bosnian President, Alija Izetbegovic, said Srebrenica would have to be evacuated. 'Evacuation means 'ethnic cleansing', ' he said. 'But faced with the creation of a new concentration camp of 50,000 people, we have to choose evacuation.'
Mr Izetbegovic's top adviser, Kemal Muftic, said in Sarajevo that the government would react positively to a complete evacuation of the city, crammed with refugees who have fled from the advancing Serbs.
The Bosnian President said he had 'no assessment' of how long the town could hold out. 'It is my personal opinion that if Srebrenica falls, then the peace plan doesn't work any more.'
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