By Marwa Rashad and Stephen Kalin

RIYADH, May 19 (Reuters) - Saudi Arabia wants to avert war in the region but stands ready to respond with "all strength and determination" following last week's attacks on Saudi oil assets, a senior official said on Sunday, adding that the ball was now in Iran's court.

Riyadh has accused Tehran of ordering Tuesday's drone strikes on two oil pumping stations in the kingdom, claimed by Yemen's Iran-aligned Houthi group. The attack came two days after four vessels, including two Saudi oil tankers, were sabotaged off the coast of the United Arab Emirates.

Iran has denied it was behind the attacks which come as Washington and the Islamic Republic spar over sanctions and the U.S. military presence in the region, raising concerns about a potential U.S.-Iran conflict.

"The kingdom of Saudi Arabia does not want a war in the region nor does it seek that," Minister of State for Foreign Affairs Adel al-Jubeir told a news conference.

"It will do what it can to prevent this war and at the same time it reaffirms that in the event the other side chooses war, the kingdom will respond with all force and determination, and it will defend itself and its interests."

Saudi Arabia's King Salman on Sunday invited Gulf and Arab leaders to convene emergency summits in Mecca on May 30 to discuss implications of the attacks.

"The current critical circumstances entail a unified Arab and Gulf stance toward the besetting challenges and risks," the UAE foreign ministry said in a statement on state news agency WAM.

Saudi Arabia's Sunni Muslim ally the UAE has not blamed anyone for the tanker operation, pending an investigation. No-one has claimed responsibility, but two U.S. government sources said last week that U.S. officials believed Iran had encouraged the Houthi group or Iraq-based Shi'ite militias to carry it out.

The Houthis, who are battling a Saudi-led coalition in Yemen, said they carried out the strike on oil pumping stations in the kingdom, which did not disrupt output or exports in the world's largest crude exporter.

A Norwegian insurers' report seen by Reuters said Iran's Revolutionary Guards were "highly likely" to have facilitated the attack on vessels near the UAE's Fujairah emirate, a main bunkering hub lying just outside the Strait of Hormuz.

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Washington has tightened economic sanctions against Iran, trying to cut Tehran's oil exports to zero, and beefed up the U.S. military presence in the Gulf in response to what it said were Iranian threats to United States troops and interests.