BAGHDAD -- Defense Secretary Ash Carter met with Iraqi leaders and his commanders Wednesday on an unannounced war zone visit aimed at broadening U.S. assistance to Iraq to defeat the Islamic State of Iraq and Syria (ISIS).

The Obama administration has been talking for days about "accelerating" the fight against ISIS, but that effort is complicated because there is some Iraqi reluctance to having a greater U.S. footprint in the country.

Those concerns could affect whether or not Iraqi leaders agree to allow the U.S. to send Apache attack helicopters and more troops into the fight.

At the start of a meeting with Prime Minister Haider al-Abadi, Carter said the U.S. wants to help Iraq as it fights against ISIS in Ramadi and then later in Mosul.

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"Everything we do...here is subject to the approval of the sovereign Iraqi government," Carter said. "And I also wanted to emphasize to you, the respect for sovereignty and for Iraq's territorial sovereignty is a principle that the United States strongly supports in every context."

Abadi said he believes Iraqi forces are making progress.

"I think we are on the verge of breaking the back of Daesh," he said, using an Arabic acronym for the ISIS group.

The Apache helicopters, said Army Col. Steve Warren, would not be used until Abadi requests them, adding that the prime minister has to balance the military options with his own political environment in the country.

Many Iraqis "don't agree with the American presence in this country," said Warren, a U.S. military spokesman.

That reluctance also could hold up any move to embed U.S. military advisers with Iraqi Brigade headquarters. The small advisory teams wouldn't be on the front lines, but would allow them to provide better planning advice and coordination for the Iraqi units, said Warren.

Because weather problems were restricting some air travel around Baghdad, Carter's meetings with Iraqi leaders were scrambled a bit, but he was eventually able to helicopter in to see Abadi and Iraq Defense Minister Khaled al Obeidi.

Carter was to talk with his commanders, including Lt. Gen. Sean McFarland who is heading the fight against ISIS, and Iraqis about the new U.S. plan to deploy a new special commando force to Iraq. It will be designed to better capitalize on intelligence in order to target, capture and kill ISIS leaders. Called an "expeditionary targeting force," the special operations troops would be used to increase the pressure on the insurgents.

Details of the plan have not been disclosed, and U.S. officials haven't said when they may deploy to Iraq.

The focus in recent days has been the battle in Ramadi, the provincial capital of Anbar province, which was taken by ISIS militants. Iraqi forces have been preparing to try to take the city back, encircling it. But progress has been slow. Warren said that Iraqi forces faced a strong counterattack from Islamic State militants on Tuesday, and lost ground for a short time. But he said they were able to eventually regain the territory and beat back the insurgents.

The Pentagon has also offered to send Apache helicopters to help the fight in Ramadi if Iraqi leaders request the aid. So far they have not.

Speaking to reporters traveling with him, Carter said the U.S. wants to use the Apache helicopters when they can "make a distinctive difference and have a strategic effect." He said he plans to discuss the offer with Iraqi leaders, adding that al-Abadi has said he is willing to consider it and any decision is up to the Iraqi government.

A senior U.S. official said the U.S. has been making preparations and will be ready at any moment to dispatch the Apaches when requested. The official was not authorized to discuss the matter publicly, so spoke on condition of anonymity.

Carter has been saying he wants to identify new ways that other coalition members can contribute to the campaign. One goal is to get allies to take on some of the missions being done by some of the approximately 3,500 U.S. troops in Iraq, so that those forces can take on more specialized roles.

Carter's trip had been planned for some time, but on Monday during a visit to the Pentagon, President Obama vowed to accelerate the campaign against ISIS, lending more urgency to the visit.