British Prime Minister Theresa May congratulated Donald Trump on winning the U.S. presidency on Wednesday, saying Britain and the United States would remain "strong and close partners on trade, security and defence".

"I would like to congratulate Donald Trump on being elected the next president of the United States, following a hard-fought campaign," May said in a statement.

"Britain and the United States have an enduring and special relationship based on the values of freedom, democracy and enterprise. We are, and will remain, strong and close partners on trade, security and defence," she said.

"I look forward to working with President-elect Donald Trump, building on these ties to ensure the security and prosperity of our nations in the years ahead."