The United States will announce new aid to war-ravaged Ukraine on Friday, consisting mainly of ammunition to help it fight against Russia's invasion force, the White House said.

"Tomorrow, just unilaterally, the US will have another round of assistance for Ukraine," National Security Council spokesman John Kirby said Thursday.

"It will include mostly ammunitions and munitions that Ukrainians will need for the systems that they already have," notably the Himars precision rocket launchers, he added.

Kirby did not provide further details.

The announcement will coincide with the visit to the White House by German Chancellor Olaf Scholz.

Western powers have promised Ukrainian President Volodymyr Zelensky they will speed up ammunition and other equipment deliveries to enable Ukraine's military to repel new offensives by Russian troops.

The European Union recently announced an effort to urgently supply 155-millimeter shells to Kyiv.