The top U.S. commander for the fight against the Islamic State group said Monday that he is skeptical of any additional military cooperation with Russia in Syria.

And he said he believes he can get the mission done without it, outlining new plans to accelerate the pace and scope of the U.S.-led coalition operations to retake the key Islamic State-held cities of Raqqa and Mosul within the next year.

In a wide-ranging telephone interview from Baghdad, Lt. Gen. Stephen Townsend said that any decision to cooperate with Moscow is one for the Obama administration to make.

But, "as a soldier, I'm fairly skeptical of the Russians," Townsend told The Associated Press. "I'm not sure how much I'm inclined to believe that we can cooperate with them."

Townsend's comments on Russia reflect a broader U.S. military reluctance to work more closely with Moscow on operations in Syria, despite requests from Russia to the U.S. to join forces against the Islamic State group in Syria. The U.S. is reluctant to cooperate with Moscow because of its alliance with President Bashar Assad; the U.S. is backing rebels who are fighting the Islamic State but who are also in Assad's sights.

Last week, U.S. aircraft scrambled twice to protect American commandos because Syrian government warplanes were bombing nearby.

The U.S. routinely speaks to the Russians in order to ensure safe flight operations over Syria and to prevent collisions. In the wake of the Syrian incidents, the U.S. sent its warning message to Syria through the Russians, who have an ongoing, closer relationship with the Syrians.

USArmy paratroopers assigned to 4th Infantry Brigade Combat Team (Airborne), 25th Infantry Division, finish boarding an Air Force C-17 Globemaster III aircraft loaded with a heavy-drop-rigged Humvee for a night jump onto Malemute Drop Zone, Joint Base Elmendorf-Richardson, Alaska. Flickr/The U.S. Army

Townsend, who took command on Sunday, also said he plans to step up the military operations in Iraq.

"We're going to strike more targets, we're going to strike them at a faster tempo," said Townsend, explaining that he wants to give the Iraqi forces the time and space to reset and prepare to retake the northern city of Mosul.

As part of that, he said he also will increase the training and equipping of Iraqi forces, including a new effort to provide combat training to Iraqi police. The police, he said, will likely face fighting as they follow Army forces into the cities and try to maintain control of the area and provide security for the citizens living there.

"In this kind of environment, even the police need some combat training like soldiers — that's something we haven't done a lot of," said Townsend, adding that the U.S. and some coalition allies will do that training.

Townsend expressed optimism that Islamic State militants will be defeated in their two main headquarters — Mosul in Iraq and Raqqa in Syria — over the next year. But acknowledging that the battles will be complicated and difficult, Townsend said it may well take the bulk of that year to meet his goals.

Russian servicemen drive a military vehicle along a road outside Kamensk-Shakhtinsky near the border with Ukraine, Rostov Region, August 17, 2014. REUTERS/Alexander Demianchuk

The Islamic State group once controlled large swaths of Iraq and Syria, and has used Raqqa as the de facto capital of the group's self-styled caliphate. But the group has suffered a string of defeats in recent months by local forces aided and backed by the U.S.-led coalition.

Townsend said he wants to retake both main cities on his yearlong watch.

"I think we may have to use all that time but, look, I'm a combat commander and I have a mission," he added. "And I don't intend to turn this over to whoever has to come behind me. It's my intent to get it done."

Iraqi officials have suggested they plan to begin the effort to retake Mosul later this fall, and the fight for Raqqa could also start within that timeline. Townsend's vow to have both retaken in the next year only underscores how difficult U.S. commanders believe it will be to drive Islamic State insurgents from those larger, heavily populated strongholds.

The United States is sending about 600 soldiers to Poland and the three Baltic states for infantry exercises, the Pentagon said, one of its highest-profile steps yet to reassure NATO allies after Russia's seizure of Crimea. Kacper Pempel/Reuters

The U.S. and Iraqi forces are establishing a logistics hub at Qayyarah air base south of Mosul, and Townsend said that American forces could begin moving to the base in the next couple of weeks. Right now construction is still being done to prepare the base and build up its defenses.

He also said that as the battle for Mosul gets closer, U.S. advisers may once again accompany Iraqi forces at the battalion level, which is closer to the fight.

Last month, the U.S. revealed that American advisers had for the first time accompanied an Iraqi battalion in order to provide advice on how to secure a temporary bridge the Iraqis had installed over the Tigris River. President Barack Obama gave commanders the authority in April to deploy advisers at the lower level headquarters, but commanders have done that sparingly so far.

"We're about to do larger operations of greater intensity so you could expect that we'll see something like that again," said Townsend Monday. "We will use that capability and authority when situations require it."

Prior to Obama's go-ahead, the U.S. military was not permitted to place advisers at echelons lower than division headquarters, which are farther from the front lines.