The Bush administration and leading Irish-American political figures have made it clear that Northern Ireland will be slipping down Washington's agenda unless progress is made quickly.
Reflecting the view of others, the SDLP leader, Mr Mark Durkan, said: "They are basically saying there is only so long they can maintain the degree of priority and attention they have had."
During the St Patrick's Day lunch on Capitol Hill, the Speaker of the US House of Representatives, Mr Dennis Hastert, made a direct appeal to Sinn Féin and the Democratic Unionist Party.
"He was close to being blunt that there have been elections in Northern Ireland, that there are two new parties in positions of leadership," Mr Durkan told The Irish Times.
"He said that it is their duty to live up to their responsibilities. He was straight about it, that the business of government is hard but it is what you have to get down to doing."
Mr Durkan said some leading congressional figures were no longer prepared to be in "the business of continually thanking Martin and Gerry for the relative peace".
"Six years is a full Senate term. It is three Congresses. We are treating it as though it is one season in the peace process," said Mr Durkan, who leaves Washington today.
"They are just making it clear that things need to happen. I think they are making that clear to the DUP and SF as well.
"They are saying: 'Yes, we're there for you, but you need to be in a better position than you are in'," Mr Durkan said.
In particular, he said, the administration and Capitol Hill were not prepared to spend years getting the DUP and Sinn Féin to a point where they would actually do business.
"They are saying: 'We cannot manage the SF/DUP positions in the way that we have managed them so far. It can't be done in that way.'
"It can't be allowed to go on to that type of timescale, which is why people are making the points that parties have mandates.
"It isn't a question now of a half-measure there, a gesture here.
"People are no longer interested in a process that is run between hints and stunts.
"They want decisive, clear, unmistakable progress," the SDLP leader said during an interview in the Senate Russell Building.
Repeating the SDLP's criticism of Sinn Féin's New York Times advertisement condemning the PSNI, Mr Durkan said: "Whatever it was intended to do it has not particularly worked for them.
"Most people here are raising the issue with us.
"People are using words like 'desperation' and all the rest of it. We are not using those words.
"People here have been saying that the Shinners are going negative and that they have not got much of a case. And they are saying that they are getting mixed messages."
Mr Alex Atwood MLA, of the SDLP, said President Bush had particularly noted the attacks on members of the North's District Policing Boards.