US Vice President Joe Biden held talks with Iraqi officials in Baghdad amid a row over a decision to bar candidates from a March election.
The prospective candidates have been banned over suspected links to Saddam Hussein's outlawed Baath party.
The move by an independent panel has outraged Sunnis who dominated Iraq for more than two decades under Saddam.
They see it as an attempt to marginalise their community, casting doubt on the inclusiveness and legitimacy of the 7 March vote.
But a US official travelling with Mr Biden, on his third visit to Iraq since US troops pulled out of urban centres in June, said he was confident the furore would be resolved by Iraqis.
'I would say based on the recent months especially, that what we've seen is a growing and significant ability of Iraqis to resolve their differences and disputes through the political process,' said Biden's national security adviser Antony Blinken.
'And so I don't think it's the place of the United States or any other outside country to resolve these kinds of problems for Iraqis because they are demonstrating they are more than capable of resolving it for themselves.'
The March election is a pivotal test of whether Iraq can sustain the growing peace and build a future of stability and prosperity on the back of multibillion-dollar deals the country has started to sign with global oil companies.
Mr Biden was asked by President Barack Obama to take the White House lead on Iraq policy.
The list contains 511 banned candidates, but is expected to get longer as more politicians are added for other reasons, such as for having criminal records or using fake university degrees.
