Sinn Fein's time as the IRA's political wing has to be wound up, a former US envoy to Northern Ireland has warned.
Richard Haass attended the breakfast event in New York
Richard Haass was speaking in New York after an event attended by Gerry Adams during his St Patrick's Day US trip.
Mr Haass said snubs by the White House and leading Irish-American Senator Ted Kennedy sent an important message.
"No-one as yet is ruling out dealing with Sinn Fein, but with the passage of months or even years, that could very well happen," he said.
"Gerry Adams does not want to become Yasser Arafat. He does not want to become someone who's unwilling to choose, (like) in Mr Arafat's case, between the olive branch and the gun.
"Mr Adams and, more broadly, the republican movement, has to make the choice 100% to play by democratic rules, to play a political game only."
Mr Haass was the special envoy to Northern Ireland in George W Bush's first administration and is now the head of a New York-based independent foreign policy think-tank.
Mr Adams is facing tough questions in the US
Mr Adams told the invited audience that the Sinn Fein leadership was determined to see the political process succeed.
"I haven't heard anyone saying we want to go back to conflict - that's the key," he said.
He said that despite any political "jockeying" or "nervousness", the "strength of the process is in the popular will of the people back home and the Sinn Fein leadership is totally wedded to making it a success".
The breakfast event was held on Monday after leading Irish-American politician Ted Kennedy said he would not meet Mr Adams during his St Patrick's Day trip to the US.
A spokeswoman for Senator Kennedy said he had cancelled a meeting because of the IRA's "ongoing criminal activity".
The move came as Sinn Fein faced increasing pressure over IRA involvement in the killing of Robert McCartney in Belfast.
Mr Adams said he was "disappointed" and Mr Kennedy had been "badly advised".
He said his party was committed to the peace process and was confident they would work with Mr Kennedy in the future.
Mr Kennedy and Mr Adams had been due to meet on Thursday.
Mr Adams has also been denied a meeting with President Bush at the White House. Instead, Mr Bush will play host to Mr McCartney's sisters.
Mr McCartney, 33, was stabbed to death after a row in a bar near the city centre on 30 January.
It is anticipated that Mr Adams will face tough questions in the US over the killing and over alleged IRA involvement in the £26.5m Northern Bank raid.