Thousands of American-trained-and-equipped Iraqi ground troops launched a long-awaited large-scale operation Monday against Islamic State militants in Anbar province, U.S. officials said.

On Monday morning, a spokesman for Iraq's Joint Operations Command, Brig. Gen. Yahya Rasool, said in a televised statement that Iraqi government forces, backed by Shiite and Sunni pro-government fighters, began an assault on Ramadi at dawn.

The role of the U.S. military was initially unclear because Rasool didn't clarify whether the U.S.-led international coalition was taking part. In the past, the U.S. military has been reluctant to support some Iraqi operations with heavy involvement of Shiite militias.

Later Monday, officials with the American-led coalition said 29 airstrikes on Sunday hit 67 targets in Ramadi linked to the Islamic State, also known as ISIS or ISIL. The list included staging areas, two excavators and an armored personnel carrier, according to a statement Monday from the Combined Joint Task Force for Operation Inherent Resolve.

Also in a statement to Military Times Monday afternoon, the U.S.-led coalition said two of the Iraqi Army brigades participating in ground operations near Ramadi were trained by coalition forces at one of several sites inside Iraq.

Those brigades, likely including several thousand troops, also received crew-served weapons, small arms and personnel protective equipment from the coalition, according to the coalition's statement. .

Additionally, coalition advisors are supporting Iraqi efforts in "operational planning, command and control, and intelligence collections," the statement said.

About 3,500 U.S. troops are deployed to Iraq, most of them tasked with training, advising and assisting Iraq forces. U.S. officials have said repeatedly that none of those American troops are or will be involved in direct combat operations.

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The assault on Ramadi comes nearly two months after militants with the Islamic State, also known as ISIS or ISIL, seized the provincial capital with a barrage of massive vehicle-borne improvised explosive devices.

This is not the first time the Iraqi government has announced an operation to retake Anbar, where several key towns, including the provincial capital of Ramadi, remain under Islamic State control. In May, authorities announced an operation to retake the city, but there has been no major progress on the ground since then.

The Islamic State, also known by the Arabic acronym Daesh, seized large parts of Anbar in early 2014 and captured Ramadi in May. Iraqi forces, which had been making steady progress against the extremists in recent months with the help of the air campaign, scored a major victory last month in recapturing Saddam Hussein's hometown of Tikrit.

In a brief statement, Iraq Prime Minister Haider al-Abadi vowed to "take revenge from Daesh criminals on the battlefield ... and their cowardly crimes against unarmed civilians will only increase our determination to chase them and to expel them from the land of Iraq."

During the past few weeks, the troops have been moving to cut the militants' supply routes and to surround and isolate Ramadi and Fallujah.

Rasool provided no further details on the ongoing operations. By noon, the country's state TV reported government forces recapturing villages and areas around Fallujah.

A top Pentagon official on Monday said the current U.S. mission is inherently limited to an advise-and-assist effort, which can restrict the U.S. military's ability to influence the situation on the ground.

"What comes with that, by definition, is that you are not directly in control. You are trying to work by, with, and through another government. ... That inherently brings challenges," said Christine Wormuth, undersecretary of defense for policy.

"As challenging as it can be at times to work with the government in Baghdad, and as challenging as it can be to see what is going on in the Iraqi security forces, we have to keep working with them," she said.

The Associated Press contributed to this report.