TEHRAN  - Iran announced new strides on Wednesday in its nuclear programme, in a defiant blow to US and EU pressure to rein in its atomic activities.

President Mahmoud Ahmadinejad unveiled on state television what was said to be Iran’s first domestically produced, 20-percent enriched nuclear fuel for Tehran’s research reactor. He also said 3,000 more centrifuges had been added to his country’s uranium enrichment effort.

Officials said new-generation centrifuges had been installed at Iran’s Natanz nuclear facility that are able to produce three times more enriched uranium. “Today we witnessed the activation of the first cascade of these centrifuges,” the head of the Atomic Energy Organisation, Fereydoon Abbasi Davani, said in a speech broadcast on state television.

“They increase Iran’s capacity to enrich uranium by three times,” he said. “This is a strong and documented response to all the sabotage conducted by the West.” The developments underlined Tehran’s determination to forge ahead with its nuclear activities despite increasingly tough sanctions from the West - and speculation that Israel or the United States could be months from launching military strikes against it.

Iran portrayed the advances as evidence it was only interested in peaceful nuclear goals, under the slogan “nuclear energy for all, nuclear weapons for none.” But the steps challenged the basis of four sets of UN sanctions and a raft of unilateral US and EU sanctions designed to halt a programme much of the West fears masks a drive for atomic weapons. Israel, which is the region’s sole but undeclared nuclear power and feels its existence is threatened by a nuclear Iran, is widely held to have been carrying out clandestine acts against its arch foe.

On Wednesday, Iran said it had finally replied to a letter sent nearly four months ago by EU foreign policy chief Catherine Ashton proposing a return to the talks. “Iran welcomes the readiness of the P5+1 group to return to negotiations in order to take fundamental steps toward further cooperation,” chief nuclear negotiator Saeed Jalili wrote in the letter, according to the official IRNA news agency. The P5+1 consists of the five permanent UN Security Council members - Britain, China, France, Russia and the United States - and Germany. Thus far, Russia and China have stood by Iran.

Meanwhile, Iran has stopped oil exports to six European states in retaliation for European Union sanctions imposed on the Islamic state’s key export, its English-language Press TV reported on Wednesday.

“Iran cuts its oil exports to six European countries,” Press TV reported.

Press TV said Iran has stopped exporting oil to Netherlands, Greece, France, Portugal, Spain and Italy.

Brent crude oil prices were up $1 a barrel to $118.35 shortly after the announcement.

The EU’s 27 member states have decided to stop importing crude from Iran from July 1 over its disputed nuclear programme.