The British Foreign Secretary, Mr Robin Cook was last night being briefed by the United Nations on an apparent breakthrough which could result in Libya handing over the two alleged Lockerbie bombers for trial.
Mr Cook, in France for the Rambouillet summit on Kosovo, was due to contact the UN Secretary General, Mr Kofi Annan, amid an atmosphere of mounting optimism that the deadlock since 1991 could now be nearing what Mr Cook called "the end game".
The Libyan leader, Colonel Muammar Gadafy, is believed to have sent a response to the UN chief which has raised hopes in New York, Saudi Arabia and South Africa, and now in Britain.
But the Libyan response is not thought to be clear-cut, and Mr Cook and Mr Annan were expected to discuss how far it amounted to an acceptance of what London and Washington are seeking. They want Libya to hand the two alleged bombers over for trial on neutral ground in The Netherlands, but by a court sitting under Scottish legal procedures, and with Scottish judges.
Crucially, Britain is insisting that if the men are convicted they must serve their sentence in Scotland. It is on this issue that there now appears to have been movement.
Two cells have already been set aside for the two suspects at Glasgow's Barlinnie jail. If convicted of murder, they would face life sentences, which are mandatory in Scotland.
Britain has said UN monitors could inspect the men's treatment in prison if they were convicted.
Mr Cook told reporters in France that when he met Saudi and South African envoys last week he delivered the "clear message" that there could not no compromise that Scotland was the place for any sentence to be served, although there could be a supervisory role for the UN at the jail.
"They reported back late last week that that could be the basis of an agreement," Mr Cook said.
"I am not going to sigh with relief until the two men touch down in The Netherlands, but I am encouraged by the progress that has been made after months of hard effort.
"It looks at last as if we could be approaching the end game."
Britain wanted justice carried out in a "fair and open trial", he said, adding: "We now look as if we are closer to that than we've ever been so far."
But even if a breakthrough was close, it could still take time for the trial to get under way at a Dutch military air base, Camp Zeist, where it is planned to be held.