RIYADH: US President Donald Trump landed in Saudi Arabia Saturday for the start of an eight-day foreign tour, taking his first steps on the world stage as scandals mount at home.

Trump can expect a warm welcome in Saudi Arabia where he is to meet King Salman and other senior royals -- in sharp contrast to Washington where pressure is building over his team's alleged links to Moscow.

Air Force One had barely taken off when it was announced that James Comey, the former FBI chief fired by Trump, had agreed to testify publicly about Russian interference in the US elections.

Reports also emerged that Trump had called Comey "a nut job" and that the FBI had identified a senior White House official as a "significant person of interest" in its probe of Russian meddling.

A red carpet was rolled out and staircase rolled up to Air Force One after it landed at King Khalid International Airport in Riyadh shortly before 9:50 am (0650 GMT).

Trump and his wife Melania, who dressed conservatively in black but did not cover her hair, walked side-by-side to the tarmac where they both shook hands with Saudi King Salman.

Trump is to hold talks with King Salman and the kingdom's two powerful crown princes later on Saturday, before giving a speech on Islam to leaders of Muslim countries on Sunday.

Sunday's speech to dozens of Muslim leaders has been touted as a major event -- along the lines of a landmark address to the Islamic world given by Obama in Cairo in 2009.

The speech will be especially sensitive given tensions sparked by the Trump administration's attempted travel ban targeting several Muslim majority nations.

I'll speak with Muslim leaders and challenge them to fight hatred and extremism, and embrace a peaceful future for their faith," Trump said ahead of his visit.

"He will encourage our Arab and Muslim partners to take bold, new steps to promote peace and to confront extremism which perpetuate chaos and violence that has inflicted so much suffering throughout the Muslim world and beyond," said Trump's National Security Adviser H.R. McMaster.

Before departing, the president tweeted he would be "strongly protecting American interests" on his marathon eight-day trip to the Middle East and Europe.

After Saudi Arabia, Trump will head to Israel and the Palestinian Territories where he hopes to revive the moribund peace process.

He then travels to Europe where he will hold face-to-face meetings including with Pope Francis and France's new leader, Emmanuel Macron.

It is a trip fraught with peril for the real estate magnate, who is known to dislike lengthy travel.

The avalanche of revelations in the run-up to his departure have eroded Trump's standing at home -- where the parallels with Richard Nixon's ill-fated presidency are now being openly drawn.

On Friday, a report by The Washington Post that the probe into his campaign's Russia ties had identified a "significant person of interest" in the White House undercut Trump's insistence his election bid had nothing to do with the Kremlin.

The White House was rocked by another bombshell when reports emerged that Trump said his firing of "nut job" Comey had relieved "great pressure" on him due to the investigation.

The scandals have revived questions about his ability to strike a presidential tone with his foreign counterparts, with Trump declaring himself the victim of the "greatest witch hunt" in American political history.

-AFP