US President Donald Trump has said he will speak with Taiwan's leader Lai Ching-te as he weighs up a potential multi-billion-dollar arms deal for the island, marking a sharp change in diplomatic procedure.

A US president has not spoken directly with a Taiwanese leader since 1979, when Washington recognised the People’s Republic of China and severed diplomatic relations with Taiwan.

Speaking to reporters on Wednesday, Trump said: "I'll speak to him. I speak to everybody. We have that situation very well in hand."

"We'll work on that, the Taiwan problem," he added.

Taiwan on Thursday said Lai would be happy to speak with Trump.