US Secretary of State Hillary Clinton discussed Saudi Arabia's role in maintaining a stable world oil supply in talks on Friday with Saudi King Abdullah, a US official said.

The United States and Saudi Arabia, the world's top oil exporter, have been strategic allies since the 1940s, but discord over how to respond to Arab popular uprisings strained relations last year.

Although the two states have mended the rift, differences persist on regional policy and how to tackle high oil prices.

The United States and other consumer countries fear Saudi Arabia may cut oil output if they release emergency reserves, neutralising their effort to cool world energy markets.

Clinton met with the king, Saudi Foreign Minister Prince Saud al-Faisal and other officials from the Gulf kingdom in Riyadh on Friday, a day before foreign ministers from across the Gulf meet with U.S. officials to discuss regional security.

"They talked about keeping the global oil supply strong in this period and the essential role that Saudi Arabia plays in that," a senior State Department official told reporters.

Diplomats and industry sources said this week that Western countries may want Clinton to seek reassurance that the Saudis will not undercut their bid to cut their fuel costs.

Oil prices have risen sharply since the start of the year, at one point breaking $128 a barrel, largely because of expanded sanctions imposed on major oil exporter Iran aimed at slowing its disputed nuclear program.

"Our shared interest in maintaining stability in oil markets was discussed" during talks between Clinton and the Saudi leader during a lengthy one-on-one meeting, the official said on condition of anonymity.

The official said that Clinton's talks with Saudi officials on Friday also included discussions of plans to enhance missile defense abilities in the Gulf, reform and the role of women in Saudi Arabia, upcoming multilateral talks about Iran's nuclear program, and Syria.

Saturday's meeting between Clinton and foreign ministers from the GCC are expected to focus at least in part on the ongoing violence in Syria, where at least 9,000 people are believed to have been killed in the year-long uprising against President Bashar al-Assad.

Clinton is expected to urge the Syria's fractured opposition to overcome divisions at a meeting of Syrian dissidents and Western foreign ministers in Istanbul on Sunday.

Saudi Arabia, with Qatar, has led Arab efforts to press Assad to end his crackdown on the uprising and step aside.

While the Obama administration is seeking ways to increase diplomatic and economic pressure on Assad, it has so far shunned calls from some US politicians to help poorly equipped rebels battling Assad forces more directly or back the kind of international military action that helped topple former Libyan leader Muammar Gaddafi last year.

Violence continued in Syria on Friday as United Nations-Arab League peace envoy Kofi Annan told Assad that his forces must be first to cease fire and withdraw.

"It's incumbent on the stronger power here to lead, and clearly it is the Assad regime that is responsible for the preponderance of the violence" in Syria, the official said.-Reuters