An Anglo-Irish summit aimed at restoring home rule to the province ended without agreement last month, despite London and Dublin saying they were close to ensuring the IRA was no longer an active paramilitary organisation.
Sinn Fein is regarded as the political wing of the Irish Republican Army (IRA).
The talks stalled over the demand of the Democratic Unionist Party (DUP) for a rewriting of the 1998 Good Friday Agreement, a peace deal which set up self-governing and power-sharing institutions between divided Protestant and Catholic communities.
"It's generally accepted that the IRA is prepared, in the context of a comprehensive agreement, to make an unprecedented and historic move forward," Sinn Fein leader Gerry Adams told BBC television on Sunday.
"But I don't see any evidence that the DUP has shifted its position."
The US-brokered Good Friday pact has largely ended three decades of conflict which claimed 3600 lives, but failed to heal deep sectarian divisions or provide stable government in the British-ruled province of 1.7 million people.
Breakdown in trust
A breakdown in trust between Protestant unionists, who support the province's political union with Britain, and Catholic republicans, who want a united Ireland, led to the suspension of the power-sharing arrangement in October 2002.
After last month's three-day summit, Britain and Ireland said they believed they had solved one sticking point that has dogged the peace process for a decade - the refusal of the IRA to fully disarm and disband - although they did not give details of what was on the table.
"It's generally accepted that the IRA is prepared, in the context of a comprehensive agreement, to make an unprecedented and historical move forward"
Sinn Fein leader Gerry Adams
But efforts to revive home rule in Belfast remain deadlocked over another issue - the demand from the DUP, led by Protestant preacher-politician Ian Paisley, for changes to the way the power-sharing legislature and executive operate.
"I think it's inevitable that we and the DUP and others will do a deal, but the only way that we can do it is on the basis of equality," Adams said.
"And I've seen no evidence of any contribution from the DUP on that issue. I hope I'm wrong in this, but I'm more and more of the view that the DUP have a longer time-frame [for reaching a deal] than the rest of us ... have in mind."