President Bush will soon have to make a tough decision about terrorism, but this time it has nothing to do with Iraq, the Middle East, or Al Qaeda. The decision concerns whether or not to register White House exasperation with the Irish peace process, and in particular the behavior of Gerry Adams, who leads Sinn Fein, the political arm of the Irish Republican Army.

Mr. Bush faces the dilemma of whether or not to invite Adams to St. Patrick’s Day celebrations at the White House, despite allegations in Ireland and Britain that the Sinn Fein leader sanctioned a huge bank robbery in Belfast just before Christmas. The robbery netted more than $51 million, making it one of the largest bank heists in history, and the police, the Northern Ireland secretary, and the Irish foreign minister have said the IRA is to blame.

It is a tough decision, because either way the president will likely come under criticism. Banning Adams, as an angry administration source hinted the president is considering, will attract hostility from Irish-Americans, a constituency the Republican Party has been wooing in recent years, with some success. But allowing him to attend will leave the White House open to accusations that it has double standards on terrorism.

Adams has been on the White House guest list for St Patrick’s Day festivities since President Clinton’s administration, and he continued to be invited after Mr. Bush took office. Adams’s inclusion has been a recognition of his role in persuading the IRA to call a ceasefire in its 20-year war to force Britain out of Northern Ireland, and it is an expression of the White House’s support for the Irish peace process.

However, pressure is growing to punish Adams, not just because the robbery of the Northern Bank in Belfast was a flagrant violation of the IRA’s commitment to peaceful activity, but also because of a widely-held suspicion that he gave the go-ahead for the heist in the midst of a major effort by the American, British, and Irish governments to secure a place for Adams’s party in the government of Northern Ireland.

Efforts to put together a stable administration – consisting of Unionists, who are mostly Protestants who wish Northern Ireland to remain part of Britain, and Sinn Fein, whose largely Catholic supporters want to break the British link – have repeatedly foundered despite the successful negotiation of the Good Friday Agreement in 1998.

The issue that has frustrated an agreement has been how to decommission the IRA’s huge stocks of weapons and explosives in a way that would convince Unionists that it had genuinely taken place. The decommissioning process has been shrouded in secrecy, and lingering skepticism about the IRA’s bona fides, along with continued IRA activity, have combined to keep the peace process in crisis.

The failure of the peace process caused the downfall of one moderate Unionist leader, David Trimble, who was prepared to share power with Adams, but who was eclipsed by the fiery Protestant preacher, the Reverend Ian Paisley.

Nonetheless, fresh talks involving Adams and Rev. Paisley began in October, based on ideas generated by the State Department’s director of policy planning, Mitchell Reiss, who doubles as the Bush envoy to the Irish peace process.

Mr. Reiss suggested that IRA decommissioning should be photographed as proof that it had happened, but that the photos be held back from publication until the new government took office and Sinn Fein was assured that the deal would hold. As this idea was being discussed, Mr. Bush phoned both Adams and Rev. Paisley, urging them to accept the plan.

The Reiss proposal won praise as a sensible compromise, but on December 8, Adams rejected it, claiming that Mr. Paisley’s goal was to humiliate the IRA. Eleven days later, armed and masked men held the families of two executives of the Northern Bank in central Belfast hostage, and the next day they forced the men to help robbers rifle the bank’s vaults.

Suspicions that only the IRA would have the skills and resources to carry out the robbery were strengthened three weeks later, when the head of Northern Ireland’s police force, Chief Constable Hugh Orde, publicly blamed the organization, setting off a storm of angry complaints about Sinn Fein and IRA duplicity.

Fueling this was the belief that Adams must have known about the planned robbery as he was talking about peace to the three governments. Although Adams has always denied being a member of the IRA, the police and seasoned observers believe he sits on the body’s ruling Army Council, which would have ordered the heist.

In the wake of the heist, the strongest words came from Irish Prime Minister Ahern: “I am upset, quite frankly, that in the period when we were in intensive talks trying to get a comprehensive agreement that people in very senior positions (in Sinn Fein) would have known what was going on.” Adams’s attempts to deny the claim have been greeted with skepticism.

Both Mr. Ahern and his British counterpart, Tony Blair, are now keeping Adams at arms-length amid calls for sanctions against Sinn Fein. Action from the Bush White House is also expected.

“This is an American administration that, for obvious reasons, does not want to be seen in any way to be turning a blind eye towards terrorism,” said a source close to Mr. Blair who spoke on condition of anonymity. “We fully understand that.”

Mr. Bush has a range of options, from returning the IRA to the State Department’s list of terrorist groups to withdrawing Adams’s permit to raise money for Sinn Fein in America, but it is unlikely either Mr. Blair or Mr. Ahern would wish him to go so far. The course of action mentioned most often, as a shot across the IRA’s bows, would be to deny Adams a visa to attend the festivities in Washington on March 17.

A senior Bush administration official acknowledged that the American government is “deeply concerned” about allegations that the IRA and Sinn Fein were involved in the robbery, and he hinted that barring Adams from the White House celebrations was a possibility.

“It is not U.S. policy to prejudge visa applications and each application is judged on its own merit at the time,” he said, but added: “Please note that Mr. Adams does not have a permanent visa entitling him to enter the United States and must apply for each visit.”

Irish-American leaders would likely react angrily to such an action. A Long Island Republican congressman and longtime friend of Adams, Peter King, said the Sinn Fein chief “should be treated by Washington the same as he has been in the past.”

It was too early, Mr. King said, to make a judgment about who was behind the robbery. Another Adams champion, Bill Flynn, who is chairman of Mutual of America and of the National Committee on American Foreign Policy, said Mr. Bush would be making “a terrible mistake” by excluding him. He blamed British ‘dirty tricks’ for the robbery, and added: “I have never known Gerry Adams…not to tell the truth.”

Other congressional supporters of Adams, including Senators Clinton, Kennedy, and Dodd, did not respond to requests for comment.