A potential nuclear deal with Iran is threatening to overshadow a meeting between the US and Gulf leaders at Camp David. Closer cooperation on military security is also expected to be a focus.
US President Barack Obama and leaders from across the Gulf states arrived at Camp David by helicopter on Thursday, before beginning one of three work sessions to be held throughout the day.
The meeting of the Gulf Cooperation Council (GCC) is supposed to be an opportunity for Obama to work on strengthening the relationship between the longtime allies.
But the president has already had to assuage fears raised by America's close negotiations with Iran over its nuclear program, with officials worried a deal with the Islamic republic could lead to destabilization in the region.
Further straining discussions is the absence of Saudi King Salman, who sent Crown Prince Mohammed bin Nayef and Deputy Crown Prince Mohammed bin Salman in his place.
Obama personally welcomed the two to the White House on Wednesday, playing down the notion of a diplomatic snub by the king.
Of the other five leaders, only two heads of state - from Qatar and Kuwait - are attending.
They are expected to discuss greater military cooperation, including holding more joint exercises and new initiatives on cyber and maritime threats.
US officials have ruled out the possibility of a formal defense treaty being introduced, similar to the one between members of NATO.
Some GCC members, worried about Tehran's potentially growing influence with the Obama administration, had hoped a pact would do more to ensure the US' commitment to them.
The Iran issue
Overshadowing the summit are anxieties over a potential agreement on curbing Iran's nuclear program.
Part of a deal would likely be the lifting of Western-imposed sanctions, and allowing the nation to access more than $100 billion (87.6 billion euros) in currently frozen accounts.
Sunni Arab leaders have also called for the US to crack down on the growing threat of extremism in the region, and what they see as Iran's tacit support for unrest in Yemen, Syria and Iraq.
Fuelling fears that Iran's confidence had grown due to a perceived strengthening of its ties to the US was news that Iranian navy ships had apparently fired warning shots at a Singaporean cargo vessel.
The incident took place off the coast of the United Arab Emirates on Thursday morning.
Also attending Thursday's meeting was Obama's secretaries of treasury, state and energy, as well as the director of the CIA.
Ben Rhodes, White House Deputy National Security Adviser, said the president's assurances the US was not switching alliances were "well received."
The US has not always enjoyed such a good relationship with Iran, with its reduced dependence on Gulf oil and perceived quickness to support democratic uprisings straining relations.
The Obama administration also leveled accusations in 2011 that the Islamic republic had planned to assassinate the Saudi ambassador to the United States in Washington.
an/cmk (Reuters, AP, AFP)