While hosting the six-nation Gulf Cooperation Council (GCC) in Washington on Wednesday and at Camp David on Thursday, President Barack Obama faces a hard sell: assuring the United Arab Emirates, Kuwait, Bahrain, Oman, Qatar and Saudi Arabia that the United States has an Iran policy that encompasses their security needs.

He must also encourage the six GCC countries to work together for their own collective security, but in a way that dovetails with America's own strategic goals.

But doing so won't be easy. Only three of the six GCC nations are sending heads of state. The leaders of Oman and the UAE pleaded health issues as their excuses to stay home; Saudi Arabia says its ruler, King Salman bin Abdul-Aziz al-Saud, won't be traveling due to humanitarian commitments to Yemen. The Saudi snub in particular reflects the concern, among America's Sunni Arab allies, that the U.S. isn't taking a hard enough stance toward Iran and its proxies.