A US plan to deploy heavy weapons and forces in Eastern Europe is still in an early planning stage, White House Spokesman Josh Earnest has said.

Earnest commented Monday for the first time on reports of the New York Times that Washington is weighing an option to send
heavy equipment to Poland and the Baltics, and also elsewhere in Eastern Europe including Romania and Bulgaria.

Poland admitted as early as Sunday there had been talks over possible deployment.

Bulgarian President Rosen Plevneliev, for his part, said on Monday the country had so far held no conversations about stationing weapons on its territory.

Earnest added the plan was in line with NATO's commitment to protect Europe.

"We signed a NATO treaty that provides for the defense of our allies and that is a treaty that the United States and this president is serious about upholding," he is heard saying in a Voice of America report.

The move would constitute the biggest deployment of US forces to newer NATO countries.

Earlier it was met with resentment from Russia, which says it might be the biggest act of aggression by the Pentagon and NATO since the Cold War ended.

This comes amid still rising tensions between the West and Russia over the situation in Ukraine.