US President George W. Bush refused on Tuesday to rule out nuclear strikes against Iran if diplomacy fails to curb the Islamic Republic's atomic ambitions.
Iran, which says its nuclear programme is purely peaceful, told world powers it would pursue atomic technology, whatever they decide at a meeting in Moscow later in the day.
Bush said in Washington he would discuss Iran's nuclear activities with China's President Hu Jintao this week and avoided ruling out nuclear retaliation if diplomatic efforts fail.
Asked if options included planning for a nuclear strike, Bush replied: "All options are on the table. We want to solve this issue diplomatically and we're working hard to do so."
Speculation about a US attack has mounted since a report in New Yorker magazine said this month that Washington was mulling the option of using tactical nuclear weapons to knock out Iran's subterranean nuclear sites.
The United States, which accuses Iran of seeking atom bombs, was expected to push for targeted sanctions against Tehran when it meets the UN Security Council's other permanent members - Britain, France, China and Russia - plus Germany in Moscow.
Russia and China oppose sanctions and the use of force.
Deputy foreign ministers from the six nations are meeting ahead of an end-April deadline for the International Atomic Energy Agency (IAEA) to report on whether Iran is complying with UN demands that it halt uranium enrichment.
"I recommend that they do not make hasty decisions, be prudent and study their path in the past. Any time they have pressured Iran they have got adverse results," Iran's Foreign Ministry spokesman Hamid Reza Asefi said.
"Whatever the result of this meeting might be, Iran will not abandon its rights (to nuclear technology)," he added later.
Iran defied UN demands by declaring last week it had enriched uranium to a level used in power stations and was aiming for industrial-scale production, ratcheting up tensions and sending oil prices to record highs above $72 a barrel.
The United States, which already enforces its own sweeping sanctions on Iran, wants the Security Council to be ready to take strong diplomatic action, including so-called targeted measures such as a freeze on assets and visa curbs.
Washington says it does not want to embargo Iran's oil and gas industries to avoid creating hardship for the Iranian people. Iran is the world's fourth-biggest oil exporter.
CHINA, RUSSIA OPPOSE SANCTIONS: China, which sent an envoy to Iran on Friday to try to defuse the stand-off, repeated a call for a negotiated solution.
"We hope all sides will maintain restraint and flexibility," Chinese Foreign Ministry spokesman Qin Gang said in Beijing.
Russia restated its opposition to punitive action. "We are convinced that neither the sanctions route nor the use of force route will lead to a solution of this problem," Foreign Ministry spokesman Mikhail Kamynin said, Itar-Tass news agency reported.
US Senator Joe Lieberman, a member of the Senate Armed Services Committee, told Israel's Jerusalem Post the United States probably could not destroy Iran's nuclear programme but could attempt to set it back by strikes as a last resort.
"I think the only justifiable use of military power would be an attempt to deter the development of their nuclear programme if we felt there was no other way to do it," he said.
In Kuwait, former Iranian President Akbar Hashemi Rafsanjani said he doubted the Americans would use force. "It is unlikely that they would enter into such a perilous situation from which they cannot come out."
Iran says it will not drop its right to enrich uranium for peaceful use but that it will work with the IAEA.
The UN nuclear watchdog says it has been unable to verify that Iran's nuclear programme is purely civilian, but has found no hard proof of efforts to build atomic weapons.
IAEA inspectors are due in Iran on Friday to visit nuclear sites, including one at Natanz where Iran says it has enriched uranium to 3.5 percent, the level used in nuclear power plants.
IRNA news agency said Olli Heinonen, ElBaradei's deputy for safeguards issues, would lead the team. One diplomat said his presence suggested Iran might provide some missing information.
Experts say it would take Iran years to produce enough highly enriched uranium for one bomb from its current 164 centrifuges. But Iran says it will to install 3,000 centrifuges, which could make enough material for a warhead in one year.