US President George W Bush is to meet the most powerful Iraqi Shia politician in Washington on Monday, officials say.
Mr Bush wants to reach out across Iraq's religious divide
Mr Bush is expected to discuss national reconciliation with the leader of the Supreme Council for Islamic Revolution in Iraq (Sciri), Abdel Aziz al-Hakim.
The group holds a majority of seats in the Iraqi parliament, and its former military wing has been accused of involvement in sectarian violence.
Mr Bush is to meet Iraqi Vice-President Tariq al-Hashimi in January.
The BBC's Nick Miles in Washington says Mr Bush wants the Iraqi authorities to take control of security across the country, and is becoming increasingly hands-on to achieve that goal.
The former armed wing of Sciri, the Badr Brigade, has merged with the army and police force but it has been accused of taking part in the torture and killing of Sunnis.
Keeping the brigade disciplined is a vital part of cooling down sectarian tension in Iraq, our correspondent says.
As part of his attempts to reach out across Iraq's religious divide, President Bush will also hold talks with Mr Hashimi, a top Sunni leader.
Next week a bi-partisan report commissioned by Congress is expected to call for a gradual US military withdrawal from Iraq.