Gerry Adams, the Sinn Fein President, is to visit Fidel Castro in Cuba at the risk of damaging the Irish republican movement's relations with Washington.

The visit, originally planned for September, is expected to take place before the end of the year. A U.S. State Department spokesman Monday said: "We would prefer the trip not to go ahead, but it is clearly Mr. Adams's decision."

The Sinn Fein leadership has been nervous about announcing details of the trip because of fears that it may have to postpone the visit at the last minute if Castro's health deteriorates.

Sinn Fein has been particularly anxious not to have to delay the visit, in case this was interpreted as a response to pressure from the White House.

Some U.S. officials had hoped the trip would be postponed indefinitely after the decision to delay the visit earlier this year and are believed to be deeply disappointed that it is now back on.

Above all, they would prefer the West Belfast legislator not to embarrass the Bush administration by meeting Castro, a sworn enemy of Washington, although they are not expected to comment formally on any such meeting.

Adams is keen to visit Cuba before the end of this year to thank Castro for his support during the 1981 hunger strikes during the twentieth anniversary of the protests, in which 10 IRA and INLA prisoners died in the Maze Prison. In September 1981 Castro announced his opposition to Margaret Thatcher's Government when he declared that "Irish patriots are writing one of the most heroic chapters in human history."

As well as meeting Castro, Adams is expected to use his trip to unveil a memorial in Havana to the IRA hunger strikers. The visit is expected to last several days.

Although Sinn Fein's standing with Washington has improved since the IRA started the process of decommissioning its guns in October, the republican movement is still smarting from the arrest of three alleged IRA volunteers in Colombia in the summer. The three, one of whom was working as Sinn Fein's representative in Cuba, are accused of using illegal documentation and of training left-wing Columbian rebels in urban terrorism.

News of the trip will also irritate Unionists in Northern Ireland. Jeffrey Donaldson, the hardline Ulster Unionist legislator for Lagan Valley, said that the proposed trip was a "timely reminder" of Sinn Fein's "Marxist tendencies."

He said: "I find it quite remarkable at times that some of the most stridently anti-Marxist Congressmen support somebody like Gerry Adams and I hope that when they see him consorting with Fidel Castro they will take time to reflect on the kind of people they are supporting."

Describing the visit as a "clear snub" to Washington, he added yesterday: "If President Bush is consistent then I think he will be wary of people like Gerry Adams in the future, and he ought to ask himself the question: 'Is a friend of Fidel Castro’s a friend of America?'" Nigel Dodds, the Democratic Unionist MP for North Belfast, said: "This all illustrates the circles in which Sinn Fein/IRA are most comfortable and I think this should come as a real eye-opener to the American people about exactly where Sinn Fein/IRA stand.

"What it will point up is that, as far as the republican movement is concerned, their affinity with the Marxist internationale is stronger than any ties to western democracy. They will know how deeply unpopular this will be with the Americans and yet they are going to go ahead with this at a time when Cuba and its policies, particularly on terrorism, are in the international dock."

He added: "It should remind Bush that, behind all the talk and rhetoric, Sinn Fein/IRA is a hardline Marxist outfit which supports revolution and that Americans would be gullible in thinking anything else about them."