Qatar's emir is skipping a Gulf Cooperation Council (GCC) summit hosted by Saudi Arabia, which has led a boycott of the country for more than a year. The bitter row between Qatar and Saudi Arabia is mired in a diplomatic crisis over the murder of journalist Jamal Khashoggi.
Other leaders of the six-nation Gulf Cooperation Council descended down a golden escalator and were greeted by Saudi King Salman ahead of Sunday's summit. Qatar sent a lower-ranking official.
Saudi Arabia, the United Arab Emirates, Bahrain and non-GCC member Egypt cut diplomatic and economic ties with Qatar in June 2017 over allegations of supporting terrorism.
Qatar, which last week abruptly announced it was withdrawing from the oil exporters' group OPEC, denies the charges and says the boycott aims to curtail its sovereignty.
Qatar's Sheikh Tamim bin Hamad Al Thani attended last year's meeting in Kuwait, where the boycotting nations sent lower-level representatives.
Bahrain's Foreign Minister Khalid Al Khalifa tweeted that Sheikh Tamim should have accepted "the fair demands and been there at the summit."
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The one-day annual gathering of leaders from the six member states is expected to focus on security issues, including the Yemen war and Iran's regional activities, and may touch on oil politics and a protracted boycott of Qatar by some neighbors.
The UAE delegation to the Riyadh summit will be headed by Prime Minister and Vice-President Sheikh Mohammed bin Rashid al-Maktoum, who is also ruler of Dubai.
The GCC -- set up in 1980 as a bulwark against larger neighbors Iran and Iraq -- groups Saudi Arabia, UAE, Bahrain, Oman, Kuwait and Qatar. Kuwait's ties with Riyadh have also been strained over control of shared oilfields.
WASHINGTON URGES UNITY
Following global outrage over the Oct. 2 murder of Khashoggi at Saudi Arabia's Istanbul consulate, Washington has increased pressure on Riyadh to end the nearly four-year-old Yemen war that has pushed that country to the brink of famine and to restore ties with Qatar for a united Gulf front against Iran.
A U.S. State Department official said on Sunday that Washington would continue to support the Saudi-led military coalition in Yemen and urged Gulf states to mend fences, including to enable a proposed new Middle East security alliance that would include the Gulf bloc, Egypt, and Jordan.
"We'd like to see that unity restored, not on our terms, but on terms of the countries that are involved," Timothy Lenderking, Deputy Assistant Secretary for Arabian Gulf Affairs, told reporters at a security forum in the UAE capital Abu Dhabi.
"It's important not only for the GCC to be a strong bulwark against Iranian influence in the Arabian Peninsula but also to allow us to capitalize on economic linkages that can add development to the region and help the countries bind together."
Qatar's exit from OPEC (after 57 years) to focus on gas appeared to be a swipe at the bloc's de facto leader: Saudi Arabia. The move has deepened the sense among diplomats and analysts that any prospect for a near-term resolution to the dispute is unlikely at Sunday's Riyadh summit.
While the boycotting states have said the row is not a priority for them and that the GCC remains valid, Doha has said the dispute harms regional security by weakening the bloc.
Relations have also soured between Saudi Arabia and Kuwait over oil production at two jointly-run oilfields in the so-called Neutral Zone, after talks in September failed to move the two countries closer to a deal.