Speaking at a memorial service for the 270 people killed in the airliner explosion 10 years ago, President Clinton vowed the perpetrators of the crime would be pursued "no matter how long it takes".

"If the suspects are not turned over by the next sanctions review [in February] ... we will seek yet stronger measures against Libya," he said.

Last week the Libyan People's Congress said it was satisfied with the plan put forward by London and Washington to try the two suspects in the Netherlands.

Libya policy unclear

There had been speculation that the men - Al Maghrahi Abdel and Khalifa Fhimah Lamen - would be surrendered in time for the anniversary.

But there has been no sign of this, and in a statement on Monday, the Libyan leader appeared to distance himself from the plan for a trial under Scottish judges.

Colonel Gaddafi called for an international court to try the two men, rather than the Scottish court sought by the US and the UK.

"An international court is the solution, with judges from America, Libya, England and other countries," he said in a Dutch television interview.

BBC Diplomatic Correspondent Barnaby Mason says Colonel Gadaffi's reluctance may be due to fears that the two men would implicate the Libyan state in the attack.

President Clinton: Ambiguous signals from Gaddafi

The men - alleged to be former intelligence officers - are accused of planting the bomb which downed Pan Am flight 103 over Lockerbie, Scotland, killing all 259 people on board and another 11 people on the ground on 21 December, 1988.

British UN Ambassador Sir Jeremy Greenstock backed Washington's call, saying: "Our patience is not unlimited. We will ask the council to look again at this issue, when it next reviews the sanctions."

President Clinton acknowledged he had been receiving "mixed signals" from the Libyan leader about the proposed trial in a Scottish court.

"But I believe there still some possibility that Libya will still accept our offer," he said.

Jim Swire: Searching for truth

Victims' families seemed optimistic about the chances of an imminent extradition of the suspects.

Dr Jim Swire, the spokesman for UK Families Flight 103, predicted that the two Libyans would be handed over for trial within weeks.

Mr Swire said he felt encouraged by a recent meeting with the UK prime minister.

"Not only do we now stand on the brink of a fair trial for the two Libyans, but our own prime minister has now assured us that our need for truth over what went wrong in 1988 will also be met," he said.