The conservative Arab monarchies of the Gulf will meet newly appointed US State Secretary John Kerry on Sunday, amid reservations over his administration's policies on Syria and Iran, analysts say.
Kerry is scheduled to meet his counterparts from the six member states of the Gulf Cooperation Council (GCC) in Riyadh, before flying on to the United Arab Emirates and Qatar.
There is "concern, frustration and disappointment about US policy. Some high GCC officials say in private they find it difficult to trust the US," said Abdulaziz Sager, chairman of the Gulf Research Centre.
The Saudi analyst spoke of "differences on key issues, including Syria, the Israeli-Palestinian conflict, Iran, and Bahrain."
Several Gulf countries, mainly Saudi Arabia and Qatar, have openly taken up the cause of the Syrian revolt and called for rebel forces to be armed in their battle against President Bashar al-Assad's regime.
Apart from refusing to arm the rebels, Washington has been "vetoing arms shipments and preventing GCC countries from helping the rebels," Sager said, calling for Washington to "at least provide intelligence sharing" with rebels.
All such shipments financed by Gulf states have been stopped, according to Dubai-based strategy analyst Mustapha Alani.
"Since September, all arms shipments financed by Gulf states have stopped because of an American veto. They want to keep control of the situation and do not want arms to fall into the hands of undesirable elements," he said.
The only exception, according to Alani, was an arms shipment reported this week by the New York Times, which said weapons bought by Saudi Arabia in Croatia were delivered to Syrian rebels through Jordan in December.
Gulf states would like to see Washington "lift its veto on arms sent to the rebels," said Sager.
"Some Gulf states, particularly Saudi Arabia and Qatar, feel the US is not going far enough or fast enough in Syria, but Kerry seems to be injecting a little more urgency in the Syrian situation," said Salman Shaikh from Qatar-based Brookings Doha Centre.
GCC countries are also concerned over US policies on their neighbour Iran and its nuclear programme.
For some Gulf countries, "Kerry is not tough enough on Iran," said Alani. "They think the United States should leave the military option on the table in case the policy of sanctions fails."
They have little faith in the US preference for sanctions to curb Iran's nuclear ambitions.
In Gulf eyes, such policies have proven to be a "failure and ineffective" in the cases of Iraq under late dictator Saddam Hussein, Sudan and in North Korea, Alani said.
Sager said the US and the GCC also had "core differences on Bahrain," where security forces boosted by Saudi-led Gulf troops crushed Shiite-dominated protests in March 2011.
"The United States sees political demands (in Bahrain) whereas GCC countries see a problem of terrorism," said Sager.
On the Israeli-Palestinian conflict, Gulf states have made no secret of their frustration at the US administration's failure to pressure its Israeli ally into a two-state solution.
For Shaikh, the Gulf monarchies, which are staunch US allies, were alarmed by "how quickly (President Barack) Obama has moved away from his old allies" in Arab Spring countries like Egypt and Tunisia.
However, Kerry, who has visited the Middle East several times in the past, could bring a change of focus
"Kerry knows the Middle East and he has a heart for the Middle East. He brings a renewed attention to the region," he said. "Kerry seems to be injecting a little more urgency in the Syrian situation."
On Thursday, at a Rome meeting with Assad's foes, Kerry announced Washington would provide $60 million in "non-lethal" assistance to support the Syrian political opposition.