Securing China's oil supplies
US officials hinted that one way Saudi Arabia could help diplomatically would be to offer China guarantees it would meet Chinese oil requirements, a step that might ease Beijing's reluctance to impose further sanctions on Iran.
China, which wields a veto on the Security Council, has lucrative commercial relationships with Iran and, along with Russia, has worked to dilute previous sanctions resolutions.
"We believe that all countries have a part to play in helping to sharpen the question for Iran," Jeffrey Feltman, the US assistant secretary of state, said.
"We would expect them [the Saudis] to use these visits, to use their relationships, in ways that can help increase the pressure that Iran would feel," he added.
Other US officials, who spoke on condition they not be identified, said they believed Saudi Arabia had made some gestures towards China on fuel assurances but gave no details.
"There have been some recent, positive moves," said one official, without elaborating.
Reviving peace talks
Clinton, who arrived in Doha on Sunday, is scheduled to meet Sheikh Hamad bin Jassim al-Thani, Qatar's prime minister. She will hold talks with King Abdullah of Saudi Arabia on Monday.
A year of US diplomatic efforts has so far failed to revive talks aimed at ending the six-decade Israeli-Palestinian conflict through a peace treaty that would create a Palestinian state in the West Bank and Gaza Strip.
Having failed to get Israel to undertake a total settlement freeze or to get Arab states to take confidence-building steps such as reopening Israeli trade offices as a first step towards negotiations, Washington now simply wants to get talks going.
Clinton planned to discuss how Arab states might give Mahmoud Abbas, the Palestinian president, political cover to help him resume peace talks despite the absence of a settlement freeze.