PSNI Chief Constable Hugh Orde will travel to Washington next week during the St Patrick's Day celebrations and will brief Irish-American politicians on recent events in Northern Ireland, according to sources on Capitol Hill.
Mr Orde is expected to make some evidence available to Congress members who have expressed concern that the IRA was being blamed for the Northern Bank robbery without due process.
Irish-Americans reacted with shock and dismay to Tuesday's IRA statement offering to shoot the killers of Robert McCartney.
Congressman Peter King, a prominent supporter of Sinn Féin leader Gerry Adams for many years, said: "It just underlines the main problem: there is no place for the IRA in a democratic society." He said there was a strong belief among Irish-American Congress members "that Gerry Adams and Sinn Féin have to separate themselves from the IRA politically and make it clear they serve no real purpose".
He declined to put a deadline on such a break, but said that at their meetings with Mr Adams in Washington next week, "there are things that will need to be discussed".
Official reaction in Washington to the IRA threat to shoot the killers of Mr McCartney was blunt.
"It's time for the IRA to go out of business," US envoy Mitchell Reiss said. Asked for his reaction, he said it was the same as everyone else's in Ireland and the US.
"We are all horrified by the statement. I think it is another indication that whatever role the IRA played in the past, it has no role to play today, tomorrow, and in all the tomorrows to come in a civilised society."
Mr Reiss confirmed he would still be meeting Mr Adams in Washington and "we will talk about recent events and how to move the peace process forward".
Asked what Sinn Féin needed to do now, the envoy said it was time for the party to say "explicitly, without ambiguity or ambivalence, that criminality would not be tolerated."
Mr Reiss stated that "all decent people need to support the rule of law and that's the strong message the McCartney sisters were sending".
Harsh reaction to the IRA statement spanned the political spectrum.
In an article in the Wall Street Journal, Dean Godson, author of a book on David Trimble, compared the Republican movement to Hizbullah and advocated that Sinn Féin/IRA be restored to the State Department's list of proscribed terrorist organisations.
In the Irish Voice, publisher Niall O'Dowd, under the headline, "IRA Have to Go Away", said that the statement was "a disastrous development" for the IRA.
He said that it had put Gerry Adams in an impossible position as he started his visit to the US "already under extreme pressure because of the breakdown in the process".
Mr Adams had no choice but to distance himself from the IRA statement, he said.