The Pentagon has downplayed speculation about U.S. and Iranian military cooperation in Iraq, hours after Secretary of State John Kerry made the suggestion in an interview. Iran, which is controlled by Shi'ite Muslims, has been alarmed by the Sunni advance not too far from its border with Iraq. Some fear that the involvement of Iran would lead to even more violence in Iraq.
Militants of the extremist group the Islamic State in Iraq and the Levant (ISIL) have taken control of several northern Iraqi cities and are moving toward the capital.
Kerry said in an interview with Yahoo Monday that President Barack Obama is considering air strikes to help the Iraqi government. He said the president will not allow insurgents to split the country.
"I do not believe the president is going to just sit by and let this take place," said Kerry.
The United States has moved four warships into the Persian Gulf, including an aircraft carrier with fighter jets and missiles.
Kerry said various ways of helping Iraq are being considered, including the use of drones and possible cooperation with Tehran. Obama has ruled out sending troops to Iraq.
"We are open to any constructive process that could minimize the violence,” said Kerry.
Iranian President Hassan Rouhani has said Tehran would cooperate with the United States on restoring security to Iraq, within the framework of international law.
But some U.S. politicians and analysts say involving Iran would only lead to more violence in Iraq. The two neighbors have a history of strained relations and fought a war in the 1980s. Tehran has undermined the U.S. mission of building a democratic Iraq governed by both Shia and Sunni Muslims, said David Schenker, an analyst at the Washington Institute for Near East Policy.
"Now we're asking them to play a productive role? This is a regime that doesn't want anything other than a dominant Shiite Iraq. And frankly, if that's what they want, they're going to foment an even larger, more bloody civil war in Iraq," said Schenker.
Thousands of people have fled the fighting in northern Iraqi cities. At a refugee camp in Kalak, Abu Qanea said he won't go back to his hometown of Mosul until he believes it's safe.
"We won't return until the situation improves and becomes safe. Once the fighters leave and the Iraqi military secures the city, the situation will improve,” said Qanea.
The swift advance of the al-Qaida-linked group in northern Iraq is threatening long-established borders in the region and raising alarm in Washington and in the neighboring countries. The United States withdrew its troops from Iraq at the end of 2011 after an almost decade-long war.