U.S. President Donald Trump on Tuesday held a phone conversation with British Prime Minister Boris Johnson over issues of trade and burden-sharing among NATO allies, the White House said in a statement.

"The two leaders again reaffirmed their commitment to strengthening the Special Relationship through a robust bilateral free trade agreement once the United Kingdom leaves the European Union," said the statement.

Trump in the phone call also stressed the need for NATO allies to robustly fund their defenses, according to the statement.

Speaking on a British radio show last week, Trump said a trade deal between Washington and London would be impossible after Brexit under the withdrawal terms Johnson reached with the European Union.

Trump, who repeatedly complained about NATO allies' free-riding on the U.S. military, is expected to visit London early December to attend the NATO Leaders' Meeting.