US Secretary of State John Kerry arrived in Saudi Arabia on Saturday hoping for an easing of tensions between the Sunni power and its predominantly Shia rival Iran.
Kerry was to attend a joint meeting with his Saudi counterpart Adel al-Jubeir and other foreign ministers from the six-nation Gulf Cooperation Council.
He will also hold talks with King Salman and his powerful son, Deputy Crown Prince Mohammed bin Salman, who is the defence minister.
Saudi Arabia and some of its allies cut diplomatic ties with Iran this month after protesters there burned Riyadh's embassy in Tehran and a consulate in the second city of Mashhad.
The violence against Riyadh's missions occurred after the kingdom executed dissident Shia cleric Nimr al-Nimr, a driving force behind anti-government protests.
Nimr was one of four Shia put to death on January 2 alongside 43 Sunnis. All were convicted of "terrorism".
"We understand the Saudi anger over the attack on their facilities in Iran," a senior US State Department official said before Kerry's arrival.
"But we also understand that lessening tensions is an important objective not only for the United States but for the region".
Saudi Arabia and its Gulf neighbours perceive a lack of US engagement in the region, particularly in the face of what they see as Iran's "interference" in Yemen, Syria and Lebanon.
Those feelings crystallised with a historic international deal which this month lifted crippling economic sanctions on Iran in return for a scaling back of its nuclear capabilities.
Kerry has long sought to reassure his Gulf allies about the overtures to Iran, and will continue those efforts in Riyadh.
During his one-day stop, Kerry is also to meet Riad Hijab, general coordinator of Syria's largest opposition coalition, ahead of UN-brokered peace talks planned with the regime of President Bashar al-Assad.
Kerry arrived from the World Economic Forum in Davos, Switzerland, and on Sunday is to continue to Laos, in Southeast Asia.