US President Barack Obama on Tuesday held the first of a string of meetings focusing partly on Syria with key Middle Eastern allies, as he met Abu Dhabi Crown Prince Mohammed bin Zayed Al-Nahayan.
The president will also meet the leaders of Turkey, Qatar and Jordan in the coming weeks, as Syrian rebels renew their appeals for Washington to provide weapons and as President Bashar al-Assad battles for survival.
After the lunch in the White House, which did not include a press photo-op, the two sides issued a statement which offered broad descriptions of the topics they covered but gave few details.
"The President and the Crown Prince ... discussed a range of regional challenges, including the need for Iran to meet its international obligations with respect to its nuclear program, the ongoing conflict in Syria, and countering the threat of violent extremism," the statement said.
Obama and his guest also noted defense, counter-terrorism and economic cooperation, the statement said, adding that the United Arab Emirates was the largest US export market in the Middle East.
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The Crown Prince, who also met Vice President Joe Biden, expressed "condolences for those who were affected by yesterday's attack in Boston."
Obama is due to meet Jordan's King Abdullah II, who he traveled to see in Amman last month, at the White House on April 26.
He will host Turkish Prime Minister Recep Tayyip Erdogan on May 16 and meet Qatar's emir, Sheikh Hamad bin Khalifa al-Thani on April 23.
Syria also topped the agenda at an Oval Office meeting between Obama and UN Secretary Ban Ki-moon last week.
Secretary of State John Kerry is due to attend a meeting of the core group of the "Friends of Syria" on April 20 in Istanbul, the State Department said last week.
The "Friends of Syria", comprising the United States, European and Arab countries opposed to Assad, held their last major meeting in Rome in February.
So far, the United States has refused to arm the rebels, fearing the weapons could fall into the wrong hands, but says it is constantly reviewing its options.