PRESIDENT Bill Clinton turned down at least three offers involving foreign governments to help to seize Osama Bin Laden after he was identified as a terrorist who was threatening America, according to sources in Washington and the Middle East.

Clinton himself, according to one Washington source, has described the refusal to accept the first of the offers as "the biggest mistake" of his presidency.

The main reasons were legal: there was no evidence that could be brought against Bin Laden in an American court. But former senior intelligence sources accuse the administration of a lack of commitment to the fight against terrorism.

When Sudanese officials claimed late last year that Washington had spurned Bin Laden's secret extradition from Khartoum in 1996, former White House officials said they had no recollection of the offer. Senior sources in the former administration now confirm that it was true.

An Insight investigation has revealed that far from being an isolated incident this was the first in a series of missed opportunities right up to Clinton's last year in office. One of these involved a Gulf state; another would have relied on the assistance of Saudi Arabia.

In early 1996 America was putting strong pressure on Sudan's Islamic government to expel Bin Laden, who had been living there since 1991. Sources now reveal that Khartoum sent a former intelligence officer with Central Intelligence Agency connections to Washington with an offer to hand over Bin Laden — just as it had put another terrorist, Carlos the Jackal, into French hands in 1994.

At the time the State Department was describing Bin Laden as "the greatest single financier of terrorist projects in the world" and was accusing Sudan of harbouring terrorists. The extradition offer was turned down, however. A former senior White House source said: "There simply was not the evidence to prosecute Osama Bin Laden. He could not be indicted, so it would serve no purpose for him to have been brought into US custody."

A former figure in American counterterrorist intelligence claims, however, that there was "clear and convincing" proof of Bin Laden's conspiracy against America.

In May, 1996, American diplomats were informed in a Sudanese government fax that Bin Laden was about to be expelled — giving Washington another chance to seize him. The decision not to do so went to the very top of the White House, according to former administration sources.

They say that the clear focus of American policy was to discourage the state sponsorship of terrorism. So persuading Khartoum to expel Bin Laden was in itself counted as a clear victory. The administration was "delighted".

Bin Laden took off from Khartoum on May 18 in a chartered C-130 plane with 150 of his followers, including his wives. He was bound for Jalalabad in eastern Afghanistan. On the way the plane refuelled in the Gulf state of Qatar, which has friendly relations with Washington, but he was allowed to proceed unhindered.

Barely a month later, on June 25, a 5,000lb truck bomb ripped apart the front of Khobar Towers, a US military housing complex in Dhahran, Saudi Arabia. The explosion killed 19 American servicemen. Bin Laden was immediately suspected.

Clinton is reported to have admitted how things went wrong in Sudan at a private dinner at a Manhattan restaurant shortly after September 11 last year. According to a witness, Clinton told a dinner companion that the decision to let Bin Laden go was probably "the biggest mistake of my presidency".

Clinton could not be reached for comment yesterday, but a former senior White House official acknowledged that the Sudan episode had been a "screw-up".

A second offer to get Bin Laden came unofficially from Mansoor Ijaz, a Pakistani-American millionaire who was a donor to Clinton's election campaign in 1996. On July 6, 2000, he visited John Podesta, then the president's chief of staff, to say that intelligence officers from a Gulf state were offering to help to extract Bin Laden.

Details of the meeting are confirmed in an exchange of e-mails between the White House and Ijaz, which have been seen by The Sunday Times. According to Ijaz, the offer involved setting up an Islamic relief fund to aid Afghanistan in return for the Taliban handing over Bin Laden to the Gulf state. America could then extract Bin Laden from there.

The Sunday Times has established that after a fierce internal row about the sincerity of the offer, the White House responded by sending Richard Clarke, Clinton's most senior counterterrorism adviser, to meet the rulers of the United Arab Emirates. They denied there was any such offer. Ijaz, however, maintained that the White House had thereby destroyed the deal, which was to have been arranged only through unofficial channels. Ijaz said that weeks later on a return trip to the Gulf he was taken on a late-night ride into the desert by his contact who told him that Clarke's front-door approach had upset a delicate internal balance and blown the deal. "Your government has missed a major opportunity," he recalls being told.

Senior former government sources said that Ijaz's offer had been treated in good faith but, with the denial of the UAE government, there was nothing to suggest it had credibility.

A third more mysterious offer to help came from the intelligence services of Saudi Arabia, then led by Prince Turki al-Faisal, according to Washington sources. Details of the offer are still unclear although, by one account, Turki offered to help to place a tracking device in the luggage of Bin Laden's mother, who was seeking to make a trip to Afghanistan to see her son. The CIA did not take up the offer.

Richard Shelby, the leading Republican on the Senate intelligence committee, said he was aware of a Saudi offer to help although, under rules protecting classified information, he was unable to discuss the details of any offer. Commenting generally, he said: "I don't believe that the fight against terrorism was the number one goal of the Clinton administration. I believe there were some lost opportunities."