The US administration has moved to shore up support among Irish Americans for its Northern Ireland policy following this week's decision to deny Sinn Féin president Gerry Adams permission to raise funds in the country.
US special envoy for Northern Ireland Mitchell Reiss appealed to prominent Irish-American political and business figures to work with the administration in promoting the peace process.
"I know that American influence will be immeasurably greater if the administration has the support of Irish America," he said. Mr Reiss was speaking in New York at a dinner for the William J Flynn Initiative for peace awards, which were given to Mr Adams and former New York governor Hugh Carey.
Washington gave Mr Adams a visa to travel to the US this week but he cancelled the trip because of the fundraising ban.
Mr Reiss, who accepted a last-minute invitation to address the dinner, praised Mr Adams as "a great leader" and promised to work closely with him.
"I wish Gerry had decided to come this evening . . . because we still have important work to do . . . In the coming weeks and months, I'll continue to work with Sinn Féin and other political parties," he said. In a letter to Mr Flynn, Mr Adams said the ban had placed him in an "invidious position" that made it impossible for him to attend the awards ceremony.
Mr Flynn, who played a key role in securing Mr Adams's first visa to visit the US in 1994, made clear his disapproval of the ban.
"I understand his inability to be here, the conflict we managed to create for him, the dilemma we placed him in," Mr Flynn said.
The US administration is impatient with Sinn Féin's refusal to endorse the Police Service of Northern Ireland and is concerned that, after the standing down of the IRA, Catholic neighbourhoods could become prey to dissident Republicans and criminal gangs.
Sinn Féin says it cannot support the PSNI until it is brought under the democratic control of locally-elected politicians in the North.
Mr Flynn said that Sinn Féin and the British government agreed on the need for "a proper policing service" in the North.
"We have got to give this new police force in Northern Ireland a chance. But it must be run by a democratic government," he said.
Mr Carey said he was disappointed that Mr Adams did not attend the dinner because he was looking forward to hearing the Sinn Féin leader declare: "The war is over."