A State Department official in Berlin, where Secretary of State Antony Blinken was holding crisis talks on Ukraine, said the United States was "expediting authorised transfers of US-origin equipment from other allies".

"European allies have what they need to move forward on additional security assistance (to) Ukraine in the coming days and weeks," the official said.

A source familiar with the authorisations said the approval was for urgent requests by Estonia, Latvia and Lithuania to assist Ukraine, a fellow former Soviet republic.

The exact amounts and types of weapons were not specified but the Baltic nations' arsenals include Javelins, portable missiles capable of destroying tanks.

Lithuanian Defence Minister Arvydas Anusauskas confirmed that his country was sending defence and other aid to Ukraine in a bid to deter Russia from attacking.

"History shows us that conceding to the aggressor eventually ends in a big war. We do not want this. Any country which is defending itself must have opportunities to do this," he told AFP.

"Our decision will contribute to the implementation of a deterrence policy," he added.

Tens of thousands of Russian troops along with tanks and artillery have been deployed near the Ukrainian border since late last year, rattling the three Baltic nations, which are members of NATO.

President Joe Biden's administration since last year has approved $650 million in weapons to Ukraine, $200 million of it last month amid fears of war.

While the Biden administration boasts that the shipments are the most ever by the United States, Ukraine has voiced hope for military supplies as quickly as possible, with shipments from nearby countries especially valuable.

Britain has also rushed anti-tank weapons to Ukraine.