President Joe Biden spoke to his Ukrainian counterpart Volodymyr Zelensky for about an hour earlier in the day as Russia refocuses its efforts eastward, the new frontline of the nearly seven-week-old war.

"The Ukrainian military has used the weapons we are providing to devastating effect," Biden said.

"As Russia prepares to intensify its attack in the Donbas region, the United States will continue to provide Ukraine with the capabilities to defend itself.

"This new package of assistance will contain many of the highly effective weapons systems we have already provided and new capabilities tailored to the wider assault we expect Russia to launch in eastern Ukraine."

Zelensky for his part tweeted that he and Biden had discussed the "additional package of defensive and possible macro-financial aid."

The new aid included some of the heavier equipment that Washington had previously refused to provide to Kyiv for fear of escalating the conflict with nuclear-armed Russia.

Pentagon number two Kathleen Hicks was due to chair a meeting Wednesday with the heads of the main American defense groups to speed up production of weapons most used by the Ukrainian army.

Before the latest package, the United States had supplied or promised Ukraine 1,400 Stinger anti-aircraft systems, 5,000 Javelin anti-tank missiles, 7,000 other anti-tank weapons, several hundred Switchblade drones, 7,000 rifles, 50 million bullets and a range of other equipment.