US President Joe Biden said Tuesday the United States would continue to supply "defensive" weapons to Ukraine against a Russian invasion and deploy US troops to reinforce NATO allies in Eastern Europe.

"I have authorized additional movements of US forces and equipment, already stationed in Europe, to strengthen our Baltic allies, Estonia, Latvia and Lithuania," Biden said in a televised speech at the White House.

"Let me be clear, these are totally defensive moves on our part."

After Biden spoke the Pentagon announced details of the move.

It said it would reposition 800 troops in an infantry battalion task force from Italy to the Baltic region and up to eight F-35 Strike fighter jets from Germany to "several operating locations along NATO's eastern flank."

Twenty AH-64 attack helicopters were to be moved from Germany to the Baltic area and 12 more would be relocated from Greece to Poland.

The steps would bolster the now more than 90,000 US troops temporarily or permanently deployed in Europe.

"These additional personnel are being repositioned to reassure our NATO allies, deter any potential aggression against NATO member states, and train with host-nation forces," a US senior defense official said in a statement.