By Angus McDowall
RIYADH (Reuters) - U.S. Secretary of State Hillary Clinton arrives in Saudi Arabia on Friday for talks to weigh limited options available to end the violence in Syria and launch a "strategic forum" with Gulf allies against a backdrop of growing tensions with Iran.
The world's main superpower and its top oil exporter have been strategic allies since the 1940s, but deep disagreements over how to tackle the Arab popular uprisings last year strained the relationship.
Although the two states have mended that rift, differences persist over both regional issues and energy policy, amid U.S. concerns that Saudi Arabia might cut oil output if consumer countries release emergency reserves, neutralizing their effort to bring down oil prices that have soared in recent months.
Topping the agenda at the talks involving Clinton, King Abdullah, Saudi Foreign Minister Prince Saud al-Faisal and other senior Gulf diplomats will be the situation in Syria, which Riyadh sees as a key to the future of the Middle East.
Backed by Western countries, Saudi Arabia has spearheaded Arab efforts to press Iranian-backed Syrian President Bashar al-Assad to end his bloody suppression of a year-old popular uprising and step aside.
The Saudis now want to see stronger action against Assad, including the arming of opposition groups, something that the United States is reluctant to do for fear of being drawn into a messy civil war.
However, it is the wider context of a regional struggle between Sunni Muslim Saudi Arabia and Shi'ite Muslim Iran that will underpin discussions over the fallout from last year's Arab Spring uprisings.
In October, the United States said it had uncovered an Iranian-backed plot to assassinate the Saudi ambassador to Washington. Iran denied any involvement in the alleged conspiracy, which was interpreted in Riyadh as part of a broad campaign being waged by Tehran against Saudi interests.
Riyadh suspects Tehran of backing unrest by neighboring Bahrain's Shi'ite majority against the island state's Sunni monarchy, supporting rebels in northern Yemen and fomenting violence among its own Shi'ite minority in eastern Saudi Arabia.
U.S. President Barack Obama initially reached out to Iran after his 2008 election. But he has since pushed for stronger sanctions against Tehran over suspicions that its nuclear energy program is a disguised bid to develop atomic bomb capability.
Saudi King Abdullah was reported to have told Washington to "cut off the head of the snake" by striking Tehran's nuclear facilities, as revealed in a 2006 U.S. diplomatic cable released by WikiLeaks.
The launch of a new "strategic forum" between the United States and allied Gulf countries, to be announced during Clinton's visit, is designed to present a united front, analysts say.
Clinton had no meeting slated with Saudi Oil Minister Ali Naimi. But oil-consuming nations are concerned that the kingdom might offset a planned release of oil stocks by the United States, Britain and France by reducing its own crude output.
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 nuclear program.
(Reporting By Angus McDowall; Editing by Mark Heinrich)