US Secretary of State Hillary Clinton is to press Saudi Arabia to help persuade China to support a tougher stand against Iran's nuclear ambitions.
Mrs Clinton will ask the Saudis to reassure China that they will meet any shortfall in its oil needs if further UN sanctions are imposed, aides say.
She will meet King Abdullah and Foreign Minister Prince Saud al-Faisal during her first visit to the kingdom.
On Sunday, she urged Iran to reconsider its "dangerous policy decisions".
Mrs Clinton told a conference in Qatar that they were leaving the international community little choice but to impose further sanctions.
The US and its allies fear Iran is attempting to develop a nuclear weapon. Iran insists its nuclear programme is entirely peaceful.
A senior state department official said on Saturday that the US wanted Saudi Arabia, which has growing trade relations with China, to persuade Beijing to abandon opposition to a fourth round of UN Security Council sanctions.
"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," Jeffrey Feltman, the acting assistant secretary for Near Eastern affairs, told reporters.
China, which wields a veto on the Security Council as a permanent member, is against imposing more sanctions.
The BBC's Kim Ghattas, who is travelling with Mrs Clinton, says Beijing fears a major loss of revenue from investments in Iran, and disruption in oil supplies from a country providing it with 400,000 barrels a day.
The secretary of state is expected to press the Saudis to reassure the Chinese that the kingdom can offset any disruption.
Mrs Clinton recently warned China that it would be "under a lot of pressure to recognise the destabilising impact that a nuclear-armed Iran would have in the Gulf, from which they receive a significant percentage of their oil".
On Sunday, US Vice-President Joe Biden said he was confident that Beijing would change its approach and back new sanctions.
In a wide-ranging speech at the US-Islamic World forum in Doha, Mrs Clinton appealed to Muslim leaders to help in halting Iran's nuclear programme, saying its policies suggested it was developing nuclear weapons.
"The evidence is accumulating that that's exactly what they are trying to do," she said. "I would like to figure out a way to handle it in as peaceful an approach possible, and I certainly welcome any meaningful engagement, but... we don't want to be engaging while they are building their bomb."
Our correspondent says Mrs Clinton's speech also seemed to appeal to Muslims and Arabs not to give up on the Obama administration.
She acknowledged there had been setbacks in re-launching peace talks between Israel and the Palestinians, and in closing the military detention centre at Guantanamo Bay, but insisted Washington was committed to achieving both.
Mrs Clinton's two deputies will head to the region in the coming days, travelling to Israel, Jordan and Egypt.
And on Monday, William Burns, the under-secretary for political affairs, will travel to Lebanon and Syria.
Our correspondent says Washington is still hoping it can loosen the links between Damascus and Tehran, while Lebanon currently holds a seat on the Security Council.
Source : http://news.bbc.co.uk/2/hi/middle_east/8515623.stm