Iraq will ask the US to keep its troops in the country beyond the 2011 withdrawal deadline set by US President Barack Obama, Leon Panetta, the White House's pick to lead the Pentagon, said.

"It's clear to me that Iraq is considering the possibility of making a request for some kind of (troop) presence to remain there," Panetta said, adding that he had "every confidence" the request would be "forthcoming at some point."

The outgoing CIA chief told the Senate Armed Services Committee on Thursday that the US should agree once the request is made.

"It really is dependent on the prime minister and on the government of Iraq to present to us what is it that they need, and over what period of time, in order to make sure that the gains that we've made in Iraq are sustained." Panetta told the committee.

Outgoing US Defence Secretary Robert Gates has publicly suggested that Iran is another reason to keep US forces in Iraq.

Washington accuses Iran of supporting Shia groups, a charge Tehran denies, and Iraqi Sunnis view Iran's intentions in Iraq with enormous suspicion.

Gates said last month that a continued US military presence in Iraq would be "reassuring" to Gulf states.

Iraqi Prime Minister Nuri al-Maliki's coalition government is debating whether to ask Washington to keep some of the 47,000 US troops in Iraq, if only in a training and advisory role.

Maliki has called for a "mutual and unified national stand" on the issue by August 1 and has criticised other groups in the coalition for either not defining their position or using the issue to attack him and other groups.

US and Iraqi military commanders are concerned Iraq's armed forces may not be fully ready to defend the country alone, with Washington pointing to gaps in Iraqi air defence, intelligence fusion, logistics and more.