"There are more Iraqi troops that will be going into Baghdad than US but both will be going in, in fairly good numbers, more than hundreds," Defence Secretary Donald Rumsfeld told reporters after meeting with Iraqi Prime Minister Nuri al-Maliki.
It's not clear if other coalition forces in Iraq such as British and Australian troops will be involved in the plan.
Mr Maliki visited the Pentagon after meeting President George W. Bush at the White House earlier in the day to discuss the plans for increased security in Baghdad, the scene of escalating sectarian violence.
The plan involves moving thousands of additional US and Iraqi troops from around Iraq and into Baghdad.
Eric Ruff, the Pentagon press secretary, said "no final decision has been made," adding that "there is a range of forces that will be arrayed within Iraq, and what that number is is still to be determined."
Iraqi security forces
Mr Rumsfeld said Mr Maliki has been consulting closely with General George Casey, the commander of the 127,000 US troops in Iraq, on the new Baghdad security plan.
Mr Maliki launched a security crackdown six weeks ago that put more US and Iraqi troops on the streets of Baghdad, but it has been engulfed by a rising tide of massacres, bombings, kidnappings and attacks.
Mr Rumsfeld would not say whether the United States also was planning to deploy additional troops to Iraq.
"US troops levels, coalition troop levels will be determined by conditions on the ground," he said.
General Casey and Mr Maliki have "fashioned this proposal which calls for some increases in Iraqi security forces, a slight change in the mix, and some changes in the Ministry of Interior approach to things," Mr Rumsfeld said.
In addition to more troops, the plan calls for embedding more US military police with the Iraqi police forces, widely regarded as corrupt and infiltrated by militia death squads.
Mr Rumsfeld said stronger intelligence, public support and stronger links between the various security ministries and coalition forces were needed to deal with the situation.
Mr Maliki "is focused very much on the reality ... that intelligence is central to success," he said.
Asked whether the situation now qualified as a civil war, Mr Rumsfeld said it was different from other civil wars in that most of the violence is centred on Baghdad and a few other provinces.
"It's a highly concentrated thing, and it is clearly being stimulated by people who would like to have what is characterized as a civil war, and win it. But I'm not going to be the one to decide if we're in it," he said.