WASHINGTON (AP) — The U.S. will send another $450 million in military aid to Ukraine, including some additional medium-range rocket systems, U.S. officials said Thursday.

The latest package will include a number of High Mobility Artillery Rocket Systems, or HIMARS, and is expected to be anounced later Thursday. The initial four HIMARS that the U.S. sent have already gone into Ukraine and are in the hand of troops there. The package will also include ammunition and other supplies.

The new aid comes just a week after the U.S. announced it will send $1 billion in military aid to Ukraine, and as the Russian military continues to slowly expand its control in the eastern Donbas region. Ukrainian leaders have persistently asked for the more advanced, precision rocket systems in order to better fight back against Russia. The officials spoke on the condition of anonymity to provide details ahead of an announcement.

The Russian military captured two villages in eastern Ukraine on Thursday and is fighting for control of a key highway in a campaign to cut supply lines and encircle frontline Ukrainian forces, according to British and Ukrainian military officials.

Russian forces have been bombarding the city of Sievierodonetskfor weeks with artillery and air raids, and fought the Ukrainian army house-to-house. The HIMARS gives Ukraine the ability to strike Russian forces and weapons from further away. The systems are mounted on trucks, which carry a container with six precision-guided rockets that can travel about 45 miles (70 kilometers).

It took about three weeks to train Ukrainian troops on the first four HIMARS, before they were moved to the fight.

The aid is part of the $40 billion in security and economic assistance passed last month by Congress and signed into law by President Joe Biden.

Overall, since the war began in late February, the U.S. has committed more than $6 billion in security assistance to Ukraine, including this latest package. The latest $450 million will be from drawdown authority, which means the Defense Department will take weapons and equipment from it’s own stock and ship them to Ukraine.