International Atomic Energy Agency chief Mohammed ElBaradei will accept an invitation to visit Iran, a UN official said yesterday, as pressure piled on Tehran to submit its nuclear facilities to tougher inspections.

The UN's nuclear watchdog last month reprimanded Iran for repeated failure to report on nuclear material, facilities and activities and called on it to sign a document allowing more intrusive, short-notice inspections of nuclear sites.

Hassan Rohani, secretary-general of the Supreme National Security Council, told visiting British Foreign Secretary Jack Straw that Iran would invite ElBaradei for "talks to remove technical problems", the official IRNA news agency reported.

In Vienna, the IAEA said ElBaradei would accept the invitation, although no date had yet been set.

"He has received the invitation and intends to respond positively," IAEA spokeswoman Melissa Fleming told Reuters.

Washington has accused Tehran of secretly trying to develop nuclear weapons. Iran says its nuclear ambitions are limited to generating electricity to meet growing demand for its 65 million people.

Russia, a key atomic energy partner of Iran, yesterday joined Western powers in urging Tehran to submit its nuclear facilities to tougher inspections.

The message was spelled out by Foreign Minister Igor Ivanov at the start of a five-day visit to Russia by the head of Iran's atomic energy programme, Gholamreza Aghazadeh.

Russia's stand on Iran's nuclear programme is significant in view of its huge assistance to Tehran in helping build its first nuclear power plant at Bushehr in the south of the country.

Russian cooperation on the Bushehr project has raised hackles in Washington which suspects Tehran of pursuing a clandestine nuclear weapons development programme - a charge denied by Iran.

A Russian statement said Ivanov told Aghazadeh that if Tehran joined the so-called Additional Protocol "it would be yet another confirmation of the peaceful character of the Iranian nuclear programme".

In Tehran, Straw also urged Iran to sign the Additional Protocol, permitting tougher inspections, immediately and unconditionally.

Failure to do so would damage international confidence in Iran and could jeopardise a possible trade agreement between Tehran and the European Union, he said.

Iranian officials appeared unmoved by Straw's warnings. While saying they had not ruled out signing the Additional Protocol, they insisted Iran should also be allowed access to Western technology to develop nuclear energy.

"Iran accepts cooperation with the IAEA but raises the question of why the members (of the nuclear Non-Proliferation Treaty) have not helped Iran in this respect," President Mohammad Khatami told Straw on Monday, state television said.

Iran argues that as a signatory of the NPT it is entitled to assistance from other NPT members for developing a peaceful nuclear power programme.

European diplomats say Iran is trying to bargain over the Additional Protocol and will not receive access to nuclear technology unless it has proved it has no intention to use it to build nuclear arms.

Rohani said that to remove any doubt about its peaceful nuclear intentions Iran was "ready to accept the participation of other big industrialised countries in its (uranium) enrichment projects," IRNA reported. Foreign Ministry spokesman Hamid Reza Asefi said Straw's visit had not brought the possibility of Iran signing the IAEA protocol any closer, but that dialogue remained open.

"We are ready to consider the concerns of European countries but it cannot be one-sided. They should clarify what will happen if we sign this protocol. Both sides should pay attention to each others' concerns," he told a news conference.