(Bloomberg) -- President Joe Biden said the US would give Ukraine as much as $600 million in additional weaponry from US stockpiles for its fight against Russia, as his administration seeks to add momentum to a recent counteroffensive by Ukrainian troops. 

The aid, which Biden announced in a memorandum to Secretary of State Antony Blinken on Thursday, would mark the 21st time the administration has drawn down US inventories to send weaponry to Ukraine since September 2021.

The previous drawdown, for $675 million, was just a week ago. 

The $600 million in assistance includes ammunition for the Himars rocket systems; 1,000 “precision-guided” 155mm artillery shells; 36,000 105mm shells; as well as mine-clearing equipment, according to a Defense Department press release issued on Thursday evening.

“Together with our allies and partners, we are delivering the arms and equipment that Ukraine’s forces are utilizing so effectively as they continue their successful counteroffensive against Russia’s invasion,” Blinken said in a separate statement.

The US and its allies want to keep the weapons flowing for that counteroffensive in which Ukraine it has taken back territory from Russian forces in the northeast Kharkiv region.

“We are moving in only one direction -- forward and toward victory,” Ukrainian President Volodymyr Zelenskiy said Wednesday during a surprise visit to the strategic city of Izyum. On Thursday, Zelenskiy said a “mass burial site” had been found there.

The Biden administration has provided Ukraine with about $15.8 billion in military aid since it took office, Blinken said.

(Updates with Defense Department press release, in fourth paragraph.)

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