President George Bush's administration has been reviewing the status of the IRA since three alleged senior members were arrested in Colombia.
The White House will also review whether Sinn Fein should be allowed to continue its fundraising and lobbying activities in the United States.
The State Department and various other agencies are investigating what the three men were doing when they were arrested, allegedly after visiting members of the Farc guerrilla group at an arms training camp. If they decide the men's activities represent a breach of its ceasefire terms, it could "designate" the group, putting an end to its profitable US fundraising – worth more than $5m (£3.5m) since 1994.
Yesterday, a State Department source said: "Things are at a very preliminary stage. We are starting to gather material. Designating a group requires detailed examination. It cannot be done overnight and is open to legal challenge."
US agencies are liaising with British authorities and there has already been a "passing of information". Britain has sent intelligence officers to Bogota to investigate whether the allegations that the three alleged IRA members were helping to train Farc – the Revolutionary Armed Forces of Colombia– in mortar and bomb-making techniques are true. The three men, James Monaghan, Martin McCauley and Niall Connolly, claim they were tourists.
While Britain has not made any formal approach to the US over the possibility of designation, officials concede it could be very damaging to the Northern Ireland peace process and would certainly not be in Downing Street's interests.
Although the US is keen to play a role in achieving peace in Northern Ireland, it is even more concerned about the role of Farc, which it believes is at odds with US interests in Latin America. In the past 20 years, more than 120 US citizens have been kidnapped in Colombia by groups including Farc.
US antipathy to Sinn Fein has grown since news of Gerry Adams' planned meeting with the Cuban leader, Fidel Castro, next month. Mr Connolly has been named by security sources in Dublin as Sinn Fein's contact in Cuba since 1996, a claim denied by the organisation.