Politicians in NI can't move on from the past, says one of President Bill Clinton's key advisers in the run-up to the Good Friday Agreement.
Northern Ireland has been without a power-sharing executive since January.
Nancy Soderberg said politicians must recognise that the peace process "is not a zero-sum game" and that mentality "needs to drive the negotiations".
A generational victim mentality was blocking prosperity, the peace process and compromise, said Ms Soderberg.
"The politicians of today are still mired in the victimisation of the past," she told the BBC's Good Morning Ulster programme.
"What I mean is, if one side wins, the other side must be losing: Both sides feel they are victims of the Troubles and therefore need to have a total victory over the other side.
'Time to step up'
"I don't know if this generation of politicians, frankly, having gone through the Troubles, is capable of stepping across that void that still exists," said Ms Soderberg.
A return to direct rule from Westminster was likely for a period, she added, but that would be a move backwards for Northern Ireland.
"It is entirely possible that you'll have short-term direct rule again, but that is a real setback to the progress that should have been happening frankly a decade ago," she said.
Former president Bill Clinton visited Northern Ireland last month and met the leaders of both the DUP and Sinn Féin.
Ms Soderberg said she talked to Mr Clinton earlier this week.
"He really feels that it's up to the parties to move forward," she said.
"The United States was the key honest broker in the 90s and through much of the years that followed his presidency, but now it's really time for them to step up and do it on their own.
"That said, he's very much cheering them on from the sidelines to try and encourage them to make progress.
"He does visit regularly, he's happy to keep an eye on it, but I think it's time for the parties to step up."
Ms Soderberg remains a high-profile Democrat in the US and is currently running for Congress. She is a former ambassador to the UN.
She said the Northern Ireland parties should not try to renegotiate the Good Friday Agreement.
"Any agreement can always be updated, there's nothing wrong with that, but right now I think that would be a distraction," she said.
"What they really need to do is have an agreement between Sinn Féin and the DUP.
"If you renegotiate the Good Friday Agreement it would look pretty much the same as what came out.
"Truly there were victims on both sides but being stuck in that mentality does no good for the future of Northern Ireland."