British Prime Minister Theresa May told President Donald Trump on Monday that U.S. tariffs imposed on EU steel and aluminium imports were "unjustified and deeply disappointing" during a phone call, her spokesman said.

"The prime minister raised the U.S. decision to apply tariffs to EU steel and aluminium imports which she said was unjustified and deeply disappointing," he told reporters.

"She said the U.S. and UK and EU are close national security allies and we recognise the importance of the values of open and fair trade across the world. The prime minister also underlined the need to safeguard jobs."