If, as widely expected, the Sinn Féin president, Mr Gerry Adams, announces he does not intend to testify before the US House of Representatives Committee on International Relations tomorrow, he will not be the first to turn down the committee's invitation.
It does not have a power to sub-poena witnesses outside the US and, for a variety of reasons, others have declined to show up.
In 2000, the Northern Secretary, Mr Peter Mandelson, changed his mind about accepting an invitation, arguing that it was inappropriate for a representative of a government to attend.
The then chairman of the committee, Mr Ben Gilman, who had wanted to question him about his suspension of the powersharing Executive, pointed out that it had previously heard from representatives of the Russian, El Salvadoran and Argentinian governments.
Among those who did attend was Mr Chris Patten, the former Tory minister and now European Commissioner, following the publication of his report on the RUC.
Mr Gilman, whose term as chair was ended by term limits, used his standing on the committee and the hearings to successfully press for the cutting off of US aid to police training in the North. It is now being restored, although under congressional scrutiny.
The committee's activism on that issue, and Mr Gilman's sponsorship of the MacBride Principles, were strongly supported by Sinn Féin backers here.
Such committee hearings form an important part of the work of both House and Senate, providing a unique platform, particularly for the chairperson, to bring a focus to pet issues.
Indeed, the right of the chair to schedule meetings and put together witness lists is the source of some resentment among junior members, not least in this case where the chairman, Mr Henry Hyde, and senior staff on the committee have been accused of pushing their own agenda and failing to consult.
A particular target of their ire, and that of Sinn Féin sympathisers, is the committee's investigative counsel, Mr John Mackey, a long-time friend of Irish issues but whose other main responsibility for the committee has been Colombia.
With the arrest in August of the three Sinn Féin supporters in Colombia, Mr Mackey suddenly found the two halves of his job uniting for the first time.
He was also overwhelmed by a new post-September 11th imperative and the desire by conservative Republicans and the administration to reinforce US support for the Colombian government.
The arrests provide them with the opportunity to demonstrate that FARC guerrillas fall within President Bush's definition of "terrorists with a global reach" and to make the case for expanding the mandate of US aid beyond the war against narcotics to war against FARC.
That has been resisted by Democrats, who are critical of the Colombian army's human rights record and its supposed links with right-wing paramilitaries responsible for many civilian deaths.
Hence the title of tomorrow's hearing: "International Global Terrorism: Its links with illicit drugs as illustrated by the IRA and other groups in Colombia."
Testimony to the committee by its invited witnesses will certainly go well beyond the IRA issue.
Those who have agreed to testify are Mr Asa Hutchinson, the administrator of the Drug Enforcement Administration, and the State Department's deputy co-ordinator for counterterrorism, Mr Mark Wong.
The Colombians have been asked to send both their chairman of the joint chiefs, Gen Fernando Tapias, and the director general of their police, Mr Luis Ernesto Gilibert. Only one is expected to attend.
Meanwhile, the State Department was yesterday holding what was described as an "in-house" seminar on its Northern Ireland policy.
Among those addressing the all-day meeting were ambassador Mr Richard Haass, the administration's "point man" on the North; Dr Paul Bew, of Queen's University; David McKittrick, of the Independent; Ms Mary Blood, of the Urban Project; and Dr Paul Arthur, of the Ulster University.
A request by The Irish Times to attend was politely turned down.