Iran on Wednesday looked to expelling the British ambassador in angry retaliation for fresh Western sanctions over its nuclear programme, which have been slammed by both China and Russia.
Iranian lawmakers, some crying "Death to Britain", adopted an emergency bill to be voted on Sunday that would downgrade diplomatic relations to the level of charge d'affaires if passed, the legislature's website said.
The bill also said parliament could take action "on other countries that behave in a manner similar to that of Britain," according to the Fars and Mehr news agencies.
Britain this week, in coordination with the United States and Canada, announced the new sanctions on Iran. They cited as justification a report by the UN atomic energy watchdog this month suggesting Tehran was researching nuclear weapons.
Britain said it was "ceasing all contact" between its financial system and that of Iran. The United States and Canada said they would also clamp down on the sector, including on Iran's central bank.
France has called for a freeze on Iranian central bank assets and an embargo on oil exports.
Britain, Canada and France have embassies in Tehran. Canada's is headed only by a charge d'affaires; the other two by ambassadors.
The United States does not have a diplomatic mission, having closed its embassy after Islamic students took its diplomats hostage in 1979 following Iran's revolution. US interests are handled by the Swiss embassy.
China on Wednesday criticised the Western sanctions, saying they would "exacerbate" the stand-off over Iran's nuclear activities.
"We believe pressuring and sanctions cannot fundamentally solve the Iranian nuclear issue. On the contrary, they will complicate and exacerbate the issue and intensify confrontation," said foreign ministry spokesman Liu Weimin.
Russia on Tuesday blasted the sanctions as "unacceptable and against international law."
China and Russia have used their weight on the UN Security Council to block any possibility of the sanctions being more broadly imposed through a UN resolution.
Iran is already subject to four sets of UN sanctions. It has rejected the UN atomic energy agency's report, and insists its nuclear programme is exclusively for peaceful, civilian purposes.
The latest sanctions put more pressure on Iran's financial sector, with the US and Britain invoking anti-terrorist laws to target the central bank and other financial institutions.
They aim to make it more difficult for Iran to be paid for its oil exports, and put pressure on Iran's currency.
They stop short, however, of hitting the central bank with more draconian measures, which Western officials and analysts feared could cause a spike in oil prices, worsening the global economic downturn and providing Iran with a revenue windfall.
Iran's representative in OPEC, Mohammad Ali Khatibi, told ISNA news agency his country could "adopt special stances" in terms of using its vast oil exports as a political tool if "emergencies and special situations demand."
He stressed, though, that Iran was not at this time changing its approach in the global oil market.
Pressure on Iran looked likely to be raised a notch on December 1, when EU foreign ministers were expected to announce additional sanctions on some 200 Iranian firms and individuals, according to diplomats.
US President Barack Obama said in a statement Monday as the latest sanctions were unveiled: "As long as Iran continues down this dangerous path, the United States will continue to find ways, both in concert with our partners and through our own actions, to isolate and increase the pressure upon the Iranian regime."
China opposes expanded sanctions against Iran
China said on Wednesday it opposed unilateral and expanded sanctions against Iran, such as those announced by several Western countries aimed at pressuring Tehran to halt its suspected nuclear weapons program.
"China is always against unilateral sanctions against Iran, let alone the expansion of such sanctions," Foreign Ministry spokesman Liu Weimin said at a regular briefing.
On Monday, the US, Britain and Canada announced more sanctions intended to isolate Iran's economy, based on International Atomic Energy Agency suspicions that Iran is secretly working to develop nuclear weapons.
But countries such as China and Russia have far greater economic investments in Iran, whose energy exports have helped it shrug off serious harm from four rounds of U.N. sanctions since 2006 and other penalties applied by individual countries and the European Union.
"We believe pressuring and sanctions cannot fundamentally solve the Iranian issue, but will complicate the issue. Ratched-up confrontation is not conducive to the region's peace and stability," Liu said, adding that the parties involved "should strengthen dialogue and cooperation."