Britain's PM Boris Johnson, US President Trump discuss united action against Saudi attacks. (File image)

British Prime Minister Boris Johnson and U.S. President Donald Trump condemned last weekend's attack on Saudi Arabian oil facilities and discussed the need for a united diplomatic response in a telephone call on Wednesday, Mr Johnson's office said.

"They condemned the attacks and discussed the need for a united diplomatic response from international partners," a statement said. "They also spoke about Iran and agreed that they must not be allowed to obtain a nuclear weapon."

A White House spokesman said in a statement the two leaders "reaffirmed the value of the special relationship in addressing shared security concerns, most notably Iran's destabilizing behavior".