Pompeo arrives in Riyadh, holds talks with Al-Jubeir

Media playback is unsupported on your device                  Media caption Syria war On the frontline with US troops fighting IS

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US Secretary of State Mike Pompeo (L) and Qatari Deputy Prime Minister and Minister of Foreign Affairs Sheikh Mohammed bin Abdulrahman Al-Thani, hold a joint press conference at the Sheraton Grand in the Qatari capital Doha, Qatar January 13, 2019.

Pompeo says Khashoggi's murder is unacceptable, and he will work to get new answers from the Saudi Crown Prince during his visit.

The relationship between Riyadh and Washington remains tense following Khashoggi's brutal slaying and dismemberment at the Saudi Consulate in Istanbul in October.

US President Donald Trump has brushed aside worldwide outrage to stand by Prince Mohammed over the murder of Khashoggi, whose corpse was dismembered inside the kingdom's Istanbul consulate. He would not comment on USA intelligence suggesting the crown prince may have ordered the killing. But they have exonerated Prince Mohammed, whose right-hand aides were allegedly involved in the murder.

"I want to talk to you about a couple of places we've been".

"It is complicated to put together, make no mistake about it, because we're talking about a complex agreement among a number of nations where we're asking for significant commitments from them", Pompeo told reporters in Abu Dhabi on Saturday.

Acknowledging that Pompeo is set to seek an update on the Khashoggi murder investigation, al-Hathloul's sister, Alia al-Hathloul, noted that, "I am struck by what is not included in Mr. Pompeo's itinerary: the fearless women activists of Saudi Arabia, who are being held in the kingdom's prisons for seeking rights and dignity".

Hathloul's sister, Loujain, is among more than a dozen activists arrested last May - just before the historic lifting of Saudi Arabia's decades-long ban on women drivers.

Pompeo has already visited United Arab Emirates, Egypt and Qatar as part of the tour.

He also called on Qatar and other Gulf Arab countries to end their worst political rift for years, which has seen Doha diplomatically and economically isolated by neighbouring former allies for the past 19 months.

US Secretary of State Mike Pompeo is in Qatar.

Bahrain, Egypt, Saudi Arabia and the United Arab Emirates, all US allies, began a boycott of Qatar over a political dispute in June 2017 that continues today.

Washington has also welcomed "Qatar's generous offer to expand critical facilities at bases used by U.S. forces in the country and to align operating procedures at these bases with North Atlantic Treaty Organisation standards, thereby increasing the operational capability of United States and coalition forces based in Qatar".

"Disputes between countries that have a shared objective are never helpful".

Attempts at mediation have stalled, as highlighted by the recent resignation of USA envoy Anthony Zinni - who quit because of an apparent "lack of will" on behalf of "regional leaders" for regional reconciliation.

"But I believe that there is a path forward where there's a set of common understandings".

"We're hoping that the unity of GCC will increase in the days and weeks and months ahead", Pompeo said, adding that Gulf unity was essential for a planned Middle East Strategic Alliance (MESA) that would also include Jordan and Egypt.