Is Saudi king's absence at Obama-hosted summit a snub?

An important summit of Gulf Arab leaders with President Obama gets underway this week without a key player: Saudi Arabia's King Salman bin Abdulaziz Al Saud. Word came just two days after the White House said he would attend the Camp David Summit of the Gulf Cooperation Council.

The Saudi government insists this is not a snub, but the last-minute cancellation is a disappointment, reports CBS News correspondent Margaret Brennan.

President Obama planned to personally reassure Arab leaders about the upcoming nuclear deal he plans to make with Iran, their long-time adversary. As CBS News chief White House correspondent Major Garrett reported, King Salman is central to the future of the U.S. relationship with the Sunni-dominated Saudi Arabia and its approach to Shia-led Iran.

Saudi Arabia, already frustrated with U.S. inaction in Syria, is concerned that Iran may carry out attacks in the region if the U.S. lifts sanctions as part of that deal.

"Fundamentally they are more concerned, more afraid of Iran than they are of al Qaeda and ISIS, and they want our total support in their struggle against Iran," CBS News senior security analyst and former CIA deputy director Michael Morell said Monday on "CBS This Morning."

To offset worry, the White House has offered to sell more weapons but stopped short of promising to militarily defend its Arab allies -- the type of security pact they seek.

"Iran wants to be the regional hegemonic power and the Sunni Arab states are pushing back against us. They want our support. I think they deserve it," Morell said.

The White House said there is no major disagreement and the Saudis claim the king needs to stay home to oversee a five-day ceasefire in its military campaign in Yemen. Morell suggested there could also be other reasons as well.

"It's very possible that in the next 24, 48 hours, we may learn that it's a health reason, for example, so we've just got to be a little bit careful," Morell said.

But the cancellation also prompted Bahrain's King Hamad bin Isa Al Khalifa to pull out.

Now only two of the six Arab monarchs invited by President Obama will meet with him this week. While their deputies will go, the fact that heads of state will not makes decision-making difficult and gives the summit less heft than the White House hoped.