"We're looking at it very seriously," Trump told reporters as he received Polish President Andrzej Duda in the Oval Office.

"Poland is willing to make a very major contribution to the United States to come in and have a presence in Poland," he said.

"If they're willing to do that, it's something we will certainly talk about," Trump added.

Such a move would fuel tensions between NATO, of which Poland is a member, and Russia, which would see a new, permanent US base so close to its borders as a threatening military expansion.