The United States maintains a strong relationship and commitment with and to the government of Iraq," White House spokesman Jay Carney said, noting Washington has been in contact with Baghdad over Iraq's efforts to defeat al-Qaida-linked groups that have been taking over parts of Fallujah and Ramadi.
"We have -- as Secretary [of State John] Kerry said -- made a significant commitment to helping the Iraqi government in dealing with that situation," Carney said. "And what Secretary Kerry's point also was -- and I think this was a broader point about conflicts in the region -- is that this is something for the Iraqis to take the lead on and handle themselves."
He said the United States has been working with Iraq to develop "a holistic strategy to isolate the al-Qaida-affiliated groups," and has seen some success defeating the Islamic State of Iraq and the Levant.
Also, the United States has accelerated foreign military sales deliveries and is looking to provide additional Hellfire missiles as early as the spring, Carney said.
Earlier Monday, Iraqi Prime Minister Nouri al-Maliki urged residents in embattled Fallujah Monday to drive out al-Qaida-linked insurgents who have seized control.
Maliki called on the people to "expel the terrorists" so "their areas are not subjected to the danger of armed clashes," state television reported.
Iraqi forces were preparing to retake the city of more than 325,000 people while hundreds fled to escape shelling and air strikes by the government, observers said.
Mowaffak al-Rubaie, a former Iraqi national security adviser, has told the BBC that defending all of Iraq from attacks by al-Qaida-linked militants is impossible.
"This can happen and probably will happen in future because you can't put millions and millions and millions of Iraqis under arms and protect every street all over the country," Rubaie said. "These guys [the militants], they are highly motivated, they are very well-trained, they can do this because they are brainwashed, their understanding of Islam is highly selective. They are brutal. They are ruthless. They are after anarchy."
Fighting also was reported in Ramadi, which like Fallujah is in Anbar province. Parts of Ramadi, the provincial capital, were controlled by militants.