Yesterday, Labour's defence spokesman, Dr David Clark, said he believed Britain, which has 11,000 troops in Bosnia, should keep about 7,500 troops there next year.
Sources in Sarajevo said that a "significant" US ground force would need to be of a similar size. The "post-I-For", or "I-For II" contingent, is likely to comprise a US, a British and probably a French brigade, totalling about 20,000 troops, about a third of the current force. Additional US troops and air support would be based in Hungary and Croatia.
The British general commanding the I-For ground forces, Lieutenant General Sir Michael Walker, said in Sarajevo yesterday that he also believed a continuing military presence would be necessary.
"There is going to have to be something around to show that the international community is still determined to prevent the war from breaking out again", he said.
"So at some stage the international community is going to have to allow a debate, which I suspect is going on behind locked doors, to come out into the open".
Speaking in Washington, the US Assistant Secretary of State responsible for Bosnian policy, John Kornblum, said it was "possible, even likely", that American troops would continue to have a role after the present I- For mandate expires on 20 December. The leading participants in the force have refused to discuss publicly what will happen after that.
But the remarks by Mr Kornblum and General Walker make it clear that the force, almost certainly run by Nato, will have to stay to preserve peace because civilian reconstruction has been slower than hoped. .
The comments from Sarajevo and Washington coincided with a report by the influential House of Commons Defence Committee, which also said a substantial contingent should remain, including British and US troops.
The committee's chairman, Michael Colvin, said it had doubts about the plausibility of the elections scheduled for 14 September, because the infrastructure was in tatters, the election data was based on the 1991 census and 80 per cent of the Bosnian population, displaced by war, was now living in the wrong place.
The committee also noted that Bosnia has placed a strain on the British army's resources, and that "in the wide range of post-Cold War scenarios in which the armed forces might be needed, either a prolonged peace-keeping mission like I-For is too large a task, or the army is too small."
The House of Commons Committee report concluded that while I-For's military tasks - the separation of the warring factions and the exchange of large areas of territory - had largely been achieved, "progress on the civil side is painfully slow".
The consequences of a precipitate decision to withdraw I-For could be "very serious. It is by no means impossible that the former warring factions will return to conflict. While not calling for an open-ended commitment, we believe that the countries participating in I-For should maintain a substantial peace-keeping force in Bosnia until more significant progress has been made in implementing the Dayton peace agreement.
"The civilian side is taking much longer to build up than we had hoped", an I-For officer in Sarajevo said yesterday. "We need to be here in strength well beyond the elections and until the elected authorities have extended their control. "