LONDON (REUTERS) - British Prime Minister Boris Johnson and US President Donald Trump said they looked forward to continued close cooperation and the negotiation of an"ambitious free trade agreement" during a phone call on Monday (Dec 16), Mr Johnson's Downing Street office said.

"The Prime Minister spoke with President Trump, who congratulated him on the result of the general election," a Downing Street spokesman said in a statement.

"They discussed the huge importance of the relationship between the UK and US, and looked forward to continued close cooperation on issues such as security and trade, including the negotiation of an ambitious free trade agreement."

Meanwhile, White House economic adviser Larry Kudlow said on Monday he would visit Britain in early January for economic and trade talks following the victory of Johnson's Conservative Party in last Thursday's election.

Johnson won the election on a pledge to take Britain out of the European Union by Jan 31. He has said he wants to negotiate a trade deal with the United States as soon as possible while also forging a new trade relationship with the EU.

Speaking to reporters at the White House, Kudlow said he and US Deputy National Security Adviser Matt Pottinger would travel to Britain "to talk about a lot of things, including trade".

"We'll probably get started on that very soon," Kudlow said, referring to the planned US-UK trade deal.

Kudlow said he had no specifics on the negotiations, but that US officials planned to tackle a British trade deal "as soon as possible".