US Secretary of State Condoleezza Rice has warned Iraqi leaders they must act quickly to settle their differences to help tackle soaring sectarian violence.
US Secretary of State Condoleezza Rice is on a tour of the Middle East
Ms Rice flew into Baghdad on an unannounced visit after talks with Israeli ministers in Jerusalem.
She met Prime Minister Nouri Maliki and other senior government officials.
The number of daily car bombs and roadside bombs in Iraq is at the highest level since the 2003 invasion, according to a US military spokesman.
Mr Maliki told state television ahead of Ms Rice's visit that security would be achieved in the next two or three months, saying the country was in the final state of "confronting the security challenge".
En route to Baghdad, Ms Rice told reporters: "Our role is to support all the parties and indeed to press all the parties to work toward that resolution quickly because obviously the security situation is not one that can be tolerated and it is not one that is being helped by political inaction.
"They don't have time for endless debate of these issues. They have really got to move forward."
The BBC's Jonathan Beale, travelling with Ms Rice, says the military transport plane was delayed by 35 minutes by "indirect fire" in the airport area.
Ms Rice, wearing body armour, was then flown in a convoy of heavily armed US helicopters to the secure Baghdad Green Zone.
Her visit comes amid confusion over whether the leader of al-Qaeda in Iraq was killed during a US military raid.
Iraqi officials are doing DNA tests on a body to determine if it is that of Abu Hamza al-Muhajir.
US military sources say it is probably not Muhajir, but they are awaiting confirmation.
The visit also comes in a week when US forces have experienced a dramatic surge in casualties.
Two US marines were killed in fighting in the western province of Anbar, the US military said on Thursday, taking to 23 the number of US service members killed since Saturday.
Earlier this week, Mr Maliki unveiled a new security initiative aimed at curbing violence.
But the BBC's Andrew North in Baghdad says the US is concerned at Mr Maliki's apparent unwillingness to take firmer action against Shia militias who are blamed for much of the violence.
More than 100 people a day are dying in sectarian violence and the US has been unable to reduce its troop numbers as hoped.