JERUSALEM — The United States will support the Iraqi government and tribes fighting al-Qaida-linked Sunni Muslim militants in Anbar province but will not send U.S. troops back to Iraq, Secretary of State John Kerry said Sunday.

Islamist militants linked to al-Qaida and tribal fighters have taken control of Ramadi and Fallujah, the main cities in the Sunni Muslim-dominated province of Anbar, which adjoins Syria, in a serious challenge to the Shiite-led government's authority.

Iraqi troops and allied tribesmen are trying to retake the province.

Speaking to reporters in Jerusalem, Kerry said the United States was concerned about events in Anbar, which was the heart of the anti-U.S. rebellion after the United States' invasion of Iraq in 2003.

While pledging to help Iraqi Prime Minister Nouri al-Maliki's government, he made clear there was no question of U.S. troops returning to Iraq. The United States withdrew its troops from Iraq in 2011 after failing to reach agreement with Maliki's government on a continuing presence.

"This is a fight that belongs to the Iraqis," he said. "We're not contemplating putting boots on the ground. This is their fight, but we're going to help them in their fight."

Kerry declined to provide details on what the United States might do to assist Maliki, whom Washington has repeatedly urged to share power with the Sunni minority — in part to prevent a renewed Sunni insurgency against the central government.

Al-Qaida's Islamic State of Iraq and the Levant (ISIL) has been steadily tightening its grip in the desert province in recent months in a bid to create a Sunni Muslim state straddling the Syrian frontier.

This week's seizure of territory in Ramadi and Fallujah was the first time in years that Sunni insurgents had taken effective control of the region's most important cities and held their positions for days.

Kerry said the violence had regional implications.

"This is a fight that is bigger than just Iraq. . . . The fighting in Syria is part of what is unleashing this instability in the rest of the region," he added.

"We can't want peace and we can't want democracy and we can't want an orderly government and stability more than the people in a particular area, in a particular country or a particular region," Kerry said. "This fight, in the end, they will have to win, and I am confident they can."

The Iraqi military's cooperation with tribesmen against al-Qaida echoes a decision by local tribes in 2006 to work with U.S. troops to fight al-Qaida forces who had taken control of most of Iraq's Sunni areas after the U.S. invasion.

U.S. troops and local tribes finally beat back al-Qaida in heavy fighting after a "surge" of U.S. forces in 2006-07.