Gerry Adams yesterday criticised US special envoy on Northern Ireland Mitchell Reiss for the "partisan" decision to ban him from fundraising while in the United States this week.
"I don't have any high regard for Mitchell Reiss's input into this process," Mr Adams told reporters at a Friends of Sinn Féin breakfast in Washington.
"If it is he who is advising the president then it is very, very bad advice."
Mr Reiss was later measured in his response, although Mr Adams remarks are understood to have caused him deep irritation.
"It is not unusual for a political leader to attack one of the governments in the course of the process," he said. "If Gerry Adams has a problem I will be meeting him later."
The Sinn Féin president described as "absurd" and "bewildering" the decision to invite him to the annual St Patrick's Day reception at the White House today, but to prevent him from raising funds for his party. This is the second time in recent months that he has been restricted in this way by the US administration.
Mr Adams said Sinn Féin would not be "bounced" or "arm wrestled" into changing its position on policing by such tactics.
The planned fundraising element of yesterday's event in a Washington hotel was dropped after the US administration denied Mr Adams the right to raise money, a move designed to increase pressure on Sinn Féin to sign up fully for the North's new policing structures.
The organisers will now refund donations given by those who attended. Up to 100 people, including several members of the US Congress, were at the event.
Mr Adams said the issue of fundraising was secondary to the principle that his party should be treated the same as all others.
"It's the principle that's involved; that Sinn Féin would be treated differently from any other party. I have to say I am just bewildered about that.
"That the British government would weeks ago have brought in legislation to give Sinn Féin, as is our right, public monies. That we can have my presence in the White House, but that I couldn't walk around the corner and go into a fundraiser. It's just bewildering and a bit bizarre."
Mr Adams said that while in the United States he was "putting it to Irish-America and to the administration that they should support our call to the British government to put the Assembly back in place".
He said he wanted the Assembly in place before the summer.