WASHINGTON, Dec 15 (AFP) - The U.S. military announced on Thursday it will expand wartime training in Germany of Ukrainian military personnel fighting Russia's invasion with a focus on joint maneuver and combined arms operations.

Pentagon spokesman Brigadier General Patrick Ryder said the training of about 500 Ukrainians a month will start in January, building on more than 15,000 Ukrainian forces trained by the United States and its allies since April.

The new training push will be on top of efforts to teach Ukrainians to operate billions of dollars worth of specialized Western military equipment that the United States and its NATO allies have provided since Russia's invasion began on Feb. 24.

"Combined arms maneuver training is a logical next step in our ongoing training efforts," Ryder said, referring to training on how to attack an enemy with multiple capabilities at once.

The 7th Army Training Command headquartered in Grafenwoehr, Germany will carry out the initiative at U.S. ranges in Germany, the Pentagon said.

Ryder said the training focus will be to use systems already in the field rather than weapons that could be delivered in the future.

Earlier this week, Reuters reported that the United States is finalizing plans to offer Ukraine the Patriot missile defense system -- one of the most advanced systems, and one which could require months of training.

Ukraine has asked its Western partners for air defenses, including U.S.-made Patriot systems, to protect it from heavy Russian missile bombardment including against its energy infrastructure.