The paper, written by the ministry's research department and sent to Israeli diplomats worldwide, said Tuesday's summit raised "questions" on North Korea's commitment to nuclear disarmament, according to private Channel 10 television.

The channel on Thursday night quoted the report as saying there were "substantive gaps between the American statements prior to the summit on the need for 'full, irreversible and verifiable' denuclearisation and the formulation of the joint statement, which only referred to North Korea's 'complete denuclearisation'."

A spokesman for the Israeli foreign ministry confirmed the veracity of the document to AFP on Friday, but refused to add further details.

Israeli Prime Minister Benjamin Netanyahu had on Tuesday commended Trump on the "historic summit," calling it "an important step in the effort to rid the Korean Peninsula of nuclear weapons."

But the Israeli foreign ministry document also pointed to doubts in Japan, South Korea, the media and US Congress as to North Korea's sincerity.

"Despite Trump's declarations about quick changes expected in North Korea's policy, the way to substantive change -- if that ever comes -- is still long and slow," Channel 10 quoted the report as saying.

Trump has sounded a triumphant tone since the summit in Singapore, where he and Kim signed a joint statement in which the North Korean leader committed "to work toward complete denuclearisation of the Korean Peninsula."

Critics have pointed to the vague wording of the non-binding document, which Trump described as a "deal", and to concerns among allies about the decision to stop US-South Korean "war games."