British Prime Minister Theresa May does "not agree" with the restrictions on immigration imposed by US President Donald Trump and will intervene if they affect UK nationals, Downing Street said Sunday.

"Immigration policy in the United States is a matter for the government of the United States, just the same as immigration policy for this country should be set by our government," a spokesman said.

"But we do not agree with this kind of approach. If there is any impact on UK nationals then clearly we will make representations to the US government about that."