The decision came despite a dispute within the administration. Mr Clinton received conflicting advice from the State Department, which wanted to bar Mr Adams, and the National Security Council, which wanted to let him in.
The visa allows Mr Adams to spend only 48 hours in the United States and specifies that he may not travel more than 25 miles outside New York. It also bans Mr Adams, who is expected to arrive this afternoon, from raising funds.
A statement from the White House said: 'The President supports this difficult decision and believes it will help advance the cause of peace in Northern Ireland.'
The United States had previously refused to give Mr Adams a visa, and, as late as last week, was still saying that he would not get one now unless he first renounced violence. The British government opposed giving him a visa but this view has carried less weight in Washington since the disclosure of its talks with Sinn Fein. Unionist politicians have refused to attend the New York conference because of the invitation.
Some 40 members of Congress - including powerful Democrats such as Senators Daniel Moynihan and Edward Kennedy - had pressed Mr Clinton to grant a visa. Final clearance only came yesterday morning at a meeting between Mr Clinton and Anthony Lake, the national security adviser, who favoured letting Mr Adams visit New York.
President Clinton is believed to have received opposite advice from the State Department which had instructed US diplomats in Belfast or Dublin to talk to Mr Adams about his views on violence. They were also to ask him about his attitude to last month's Downing Street declaration. The stipulations were geared to denying him a visa.
Last year Mr Clinton offended Irish-Americans who had supported him in the presidential election by twice denying Mr Adams a visa.
Mr Adams said on Irish television last night that it was 'my belief we will now succeed' in bringing about peace. The drive for peace was now 'a central part' of Sinn Fein's existence. But he said London and Dublin had, at least in private, to agree a common policy objective towards resolving the Northern Ireland problem.
A Downing Street spokesman said: 'Gerry Adams has said that he wants to end violence and embrace the joint declaration. It is on that basis that we understand the visa was granted. Sinn Fein and the IRA will be judged on their deeds.' But a Unionist MP, John Taylor, denounced the move, accusing Mr Clinton of yielding to the 'Irish lobby'.
At the weekend Albert Reynolds, the Irish premier, wrote to Mr Adams giving further clarification of key points in the Downing Street declaration and, it is believed, the process by which Republicans could be assimilated into constitutional politics after a permanent IRA ceasefire.Reuse content