Under Secretary of Defense Colin Kahl said Ukraine forces need about three weeks of training to be able to use the Himars, a highly mobile guided rocket launcher that could give the Ukrainians a distance and accuracy edge in the grinding artillery battle in the Donbas region.

Carrying six rockets at a time with ranges of more than 70 kilometers (42 miles), double that of US howitzers already in use on the battlefield, the Himars system "will provide Ukraine with additional precision in targeting at range," Kahl told reporters.

Under the new aid package, the Ukrainian military will also receive five counter-artillery radars, two air-surveillance radars, 50 command launch units for the Javelins, 6,000 other anti-armor weapons, 15,000 artillery rounds, and 15 tactical vehicles.

This latest package takes the total amount of US security assistance for Ukraine since Russia invaded on February 24 to $4.6 billion.

"Our support for Ukraine and that of the international community remains unwavering," said Kahl.

Kahl said that the Himars systems, which Kyiv has been requesting for weeks, were already prepositioned in Europe for training and then delivery. In addition to the three weeks operations training, he said maintaining the equipment could require two more weeks.

They would be very useful for Ukraine forces to single out and strike high-value Russian targets, he said.

He confirmed that Ukraine's President Volodymyr Zelensky had provided Washington assurances that the Himars would not be used to strike targets inside Russia, responding to US worries that doing so could incite Moscow to expand the war beyond Ukraine.

"President Biden has made clear we have no intention of coming into direct conflict with Russia," said Kahl.