WARSAW: US Defense Secretary Lloyd Austin on Friday said Washington was seeing "more" Russian forces moving into the Ukraine border region, despite Moscow's announcement of withdrawals.

"Although Russia has announced that it is moving its forces back to garrison, we have yet to see that," Austin told reporters in Warsaw alongside Polish Defence Minister Mariusz Blaszczak.

"In fact, we see more forces moving into that region, that border region," he said, adding the United States had also observed Russian activity such as "moving closer to the border, dispersal of troops, increasing logistical capabilities."

"All of the indicators continue to indicate that he (Russian President Vladimir Putin) will maintain the capability to launch an attack."

Russia announces end of Crimea military drills, troops leaving

Austin spoke after Russia announced Friday that it was withdrawing more tanks and other armoured vehicles from areas near Ukraine's border after running war games that raised concerns in the West.

Later Friday, US President Joe Biden is expected to hold talks with Western allies to discuss Ukraine as fears swirl Russia could be seeking to create a pretext to invade.

"There is still time and space for diplomacy," Austin said.

"The United States in lockstep with our allies and partners, including Poland, has offered Mr Putin a path away from crisis and towards greater security."

The defense secretary also confirmed that the United States planned to sell 250 Abrams tanks to Poland, although added that the exact timing of delivery was still in the works.

US says more Russian troops mass near Ukraine, invasion could come at any time

The United States is in the process of temporarily deploying around 4,700 additional soldiers to EU and NATO member Poland in response to Russia's troop build-up around Ukraine.

This reinforcement will bring the US military presence in Poland to around 10,000 troops on rotation.