US President Donald Trump accused several European allies on Monday of failing to support the United States during its confrontation with Iran, ahead of a visit to Washington by NATO Secretary General Mark Rutte.

Axar.az reports, citing foreign media, that Trump said at the White House that the US had spent vast sums over the years helping to protect Europe, but that key allies had not stood by Washington when it sought support during the conflict with Iran.

He singled out the United Kingdom, Germany and Italy, saying: "We asked them to come, and they weren't there for us."

Trump did not provide details of the support the US had sought.

US officials have repeatedly criticized NATO allies for what they described as insufficient support during the war with Iran.

Trump also appeared to question future US security commitments to Europe.

He said Washington spent "hundreds of millions of dollars a year" helping to protect European countries from Russia and suggested the US could be less willing to assist allies in the future if they were unwilling to offer support "on small stuff."

Rutte is expected to visit Washington from Tuesday to Thursday. His schedule includes a meeting with Trump at the White House as well as talks with other senior US officials.