Sinn Féin president Gerry Adams will not travel to the US next week unless he is allowed to raise funds during his visit, the party said yesterday.
The US administration has indicated that Mr Adams will be granted a visa to visit the country to promote the peace process, but Washington has yet to decide if he will be allowed to speak at fundraising events.
Sinn Féin's chief negotiator Martin McGuinness said that a fundraising ban would be a "wholly negative" move that would encourage the Democratic Unionist Party (DUP) to undermine the Belfast Agreement.
"If Gerry Adams is banned from addressing US citizens at fundraising events next week he will not travel to the United States. Of course, he and others in the Sinn Féin leadership will continue to engage with US opinion and he will travel there as part of that engagement in the time ahead," he said.
US special envoy to Northern Ireland Mitchell Reiss said this week he hoped Mr Adams would visit Washington, but declined to comment on the visa issue.
Some elements within the administration believe Mr Adams should be refused entry into the US altogether until he makes positive statements about the Police Service of Northern Ireland.
Mr Adams will almost certainly hear on Monday that he has been granted a visa to visit the US the following day. But it remains unclear if Washington is ready to drop its ban on visiting Sinn Féin politicians raising funds, which was imposed in January after the Northern Bank robbery and the murder of Robert McCartney.
The administration said this week that lifting the ban was not conditional on Sinn Féin making a commitment to join the North's policing board. However, Washington has made no secret of its impatience with Sinn Féin over policing.
Mr McGuinness warned that linking the issue of policing with permission to raise funds in the US would be counterproductive and could call into question Washington's approach to the political process in the North.
"The US has played a pivotal role in the creation and evolution of the peace process. An even-handed approach has been the hallmark of success in this. All parties have been treated equally.
"However, any heavy-handed attempt by the State Department to try and dictate Sinn Féin policy on policing is misguided and will do nothing to help in the resolution of this key issue." he said.
Mr Adams is due to receive an award from the National Committee on American Foreign Policy on Tuesday at a dinner hosted by Irish-American businessman Bill Flynn, who has played a prominent role in the peace process.
A Sinn Féin spokesperson said Mr Adams would greatly regret missing the chance to accept the award and to thank Mr Flynn and the Irish-American community for their role in the political process in the North. Mr Adams is also due to address a fundraising dinner hosted by Friends of Sinn Féin, one of a number of events in what is traditionally the party's busiest fundraising month in the US.
"These fundraising events allow supporters of Irish unity to contribute to Sinn Féin's political programme to achieve this through peaceful and democratic activity. Such support is entirely legitimate and indeed necessary in demonstrating that politics works," Mr McGuinness said.