U.S. Secretary of State Hillary Clinton met Saudi Arabia's king and foreign minister in Riyadh on Friday to discuss the Syria conflict against a backdrop of tension with Iran and oil policy differences. The world's main superpower and its top oil exporter have been strategic allies since the 1940s, but discord over how to respond to Arab popular uprisings strained relations last year. "Both sides have recognized that their common interests are much more significant than the issues that have recently been dividing them," said Robert Jordan, U.S. ambassador to Riyadh from 2001-03, citing anti-terrorism cooperation, concerns over a nuclear Iran and wider Middle East stability. 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, neutralizing their effort to cool world energy markets. Diplomats and industry sources said 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. Saudi Arabia says it also wants to reduce oil prices, but that the last stocks release failed to do so and that it is already meeting all demand for its crude.