US President Donald Trump's keenly awaited decision on whether to move the US embassy in Israel from Tel Aviv to Jerusalem will not come by a Monday deadline, the White House said.

"The president has been clear on this issue from the get-go: It's not a matter of if, it's a matter of when," said White House spokesman Hogan Gidley hours before the administration's decision was due.

Trump was theoretically due Monday to decide whether to sign a legal waiver delaying by six months plans to move the US embassy to Jerusalem -- as successive administrations have done at regular intervals for more than two decades.

"No action though will be taken on the waiver today and we will declare a decision on the waiver in the coming days," Gidley said