Top negotiator Saeed Jalili said Iran was ready to rejoin EU-led talks with major powers on assuaging Western concerns over its nuclear programme even as tensions with the United States soared in the Gulf.

"We will give a resounding and many-pronged response to any threat against the Islamic Republic of Iran," Jalili told Iranian diplomats gathered in Tehran in comments reported on Saturday.

But both he and other officials left the door open to resuming long-stalled talks led by European Union foreign affairs chief Catherine Ashton on Western concerns over Iran's nuclear programme.

"We officially told them to come back to the negotiation based on cooperation," Jalili said.

Iran's ambassador to Germany, Alireza Sheikh-Attar, told the Mehr news agency on Saturday: "We will soon send a letter, after which (new) talks will be scheduled."

Foreign Minister Ali Akbar Salehi was also quoted by a website of the state broadcaster as telling a visiting Chinese foreign ministry official that "Iran is prepared for the continuation of nuclear negotiations" on the basis of a Russian proposal.

Iran is subject to four rounds of UN sanctions over its nuclear programme, which many Western governments fear is cover for a drive for a weapons capability, an ambition Tehran denies.

The United States and its allies have also imposed unilateral sanctions on Iran's economy.

The last lot of unilateral sanctions triggered a demonstration in Tehran that led to members of the Basij militia controlled by the Revolutionary Guards ransacking the British embassy.

London reacted by closing the mission and ordering Iran's embassy in Britain closed.

More sanctions are on the way.

US President Barack Obama is expected to sign into law soon additional restrictions on Iran's central bank, which acts as the main conduit for Iranian oil sales.

The European Union is considering other measures that could include an embargo on Iranian oil imports, with foreign ministers to meet on the issue in a month's time.

Iran's oil minister, Rostam Qasemi, told the Aseman weekly that sanctions "will drive up the price of oil to at least $200" per barrel.

Tehran has warned that if the threatened sanctions are implemented it will consider closing the Strait of Hormuz, a strategic waterway through which more than a third of the world's tanker-borne oil supplies pass.