US President Barack Obama (L) shakes hands with Saudi Arabia's King Salman at the start of a bilateral meeting at Erga Palace in Riyadh, in this January 27, 2015 file photo. [Photo/Agencies]

WASHINGTON/RIYADH - The White House scrambled on Monday to counter perceptions that the Saudi king's absence from a summit later this week could undermine US efforts to assure Gulf states it remains committed to their security against Iran.

King Salman's abrupt decision to skip the US-hosted regional talks shows how Gulf rulers, displeased by what they see as US indifference to Iranian meddling in the Arab world, may hesitate to bless any final nuclear deal that President Barack Obama reaches with Tehran.

Some analysts and diplomats in the Middle East and Washington interpreted Salman's decision to stay away from the meeting at the Camp David presidential retreat as a diplomatic snub, despite denials from US and Saudi officials.

Riyadh announced the monarch's no-show on Sunday, only two days after the White House had said he would attend the summit of Gulf Cooperation Council (GCC) states - some of which have long doubted Obama's commitment to confronting Iranian backing of Shi'ite Muslim militias across the region.

Crown Prince Mohammed bin Nayef, who has strong ties with the US political and security establishment, will represent Saudi Arabia at the May 13-14 gathering along with Deputy Crown Prince Mohammed bin Salman, the king's son who serves as the defence minister. Since Salman took power in January, the pair have determined most aspects of Saudi policy.

Only two of the Gulf countries - Kuwait and Qatar - will be represented by their ruling monarchs, while the others are all sending lower-ranking officials.

US officials quickly pushed back against the notion that Gulf Sunni Muslim allies downgraded their attendance to signal dissatisfaction with Obama's diplomacy with Shi'ite Iran ahead of an end-June deadline for a landmark nuclear deal.

The White House announced that Obama had spoken by phone to Salman on Monday, apparently trying to show that relations remained on a solid footing.

Ben Rhodes, Obama's deputy national security adviser, said the administration was convinced that the president would have "the right group of people around the table" at Camp David. "These are the people responsible for the security portfolios," he told reporters in a pre-summit briefing.

The Saudi government said one of the main reasons Salman was skipping the summit was because it overlapped with a five-day humanitarian ceasefire in neighboring Yemen, where a Saudi-led coalition is waging a bombing campaign against Iran-allied Houthi rebels.

The leading Gulf Arab power has complained for years that Washington does not take its concerns seriously. It thinks a focus on settling the dispute over Tehran's nuclear program has distracted the United States from more urgent problems and raised questions about broader security commitments to the region.