WASHINGTON (Reuters) - Another 50 U.S. special operations forces have arrived in Baghdad under the newly appointed command of a two-star general as the U.S. military steadily ramps up an advisory mission aimed at helping Iraq battle back Sunni militants, the Pentagon said on Thursday.

The Pentagon said the first of two planned Joint Operations Centers in Iraq had also become activated, bolstering its ability to oversee U.S. teams and gather information about the situation on the ground, including about Iraq’s security forces.

“It will of course serve as a fusion center where information that’s coming in from the various teams can be consolidated and it can be analyzed,” said Colonel Steve Warren, a Pentagon spokesman.

Iraq’s million-strong army, trained and equipped by the United States, largely evaporated in the north after Sunni fighters led by the Islamic State in Iraq and the Levant launched their assault with the capture of the north’s biggest city Mosul on June 10.

But in recent days, government forces have been fighting back, relying on elite commandos flown in by helicopter to defend the country’s biggest oil refinery at Baiji. [ID:nL6N0P71FL]

With the arrival of the additional 50 forces, which the Pentagon said happened late on Wednesday, a total of about 180 of the up to 300 U.S. military forces ordered into Iraq by Obama are already on the ground. They are expected to take two to three weeks to carry out a preliminary assessment.

Information they provide will be complemented by information gleamed by regular manned and unmanned reconnaissance flights over Iraq - about 30 to 35 per day according to the Pentagon.

Obama has not ruled out additional action in Iraq, including air strikes.

The Iraq advise-and-assist mission was put under the command of Major General Dana Pittard, who is leading the newly named “Joint Forces Land Component Command, Iraq,” the Pentagon said.

The U.S. military also plans to establish a Joint Operations Center in northern Iraq but Warren did not disclose details on timing.