Israel on Saturday denounced Iran's fueling up of its first nuclear power plant as "totally unacceptable" and called for more international pressure to force Tehran to cease any uranium enrichment.

Israel, widely assumed to be the only Middle East country to have nuclear weapons, has said a nuclear-armed Iran would be a threat to its existence, raising concerns Israel could attack Iran's nuclear sites.

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In a statement issued after the Islamic Republic celebrated the launch of its reactor in Bushehr, Israeli Foreign Ministry spokesman Yossi Levy said: "It is totally unacceptable that a country that so blatantly violates resolutions of the (United Nations) Security Council, decisions of the International Atomic Energy Agency and its commitments under the NPT (non-proliferation treaty) should enjoy the fruits of using nuclear energy."

"The international community should increase pressure on to force Iran to abide by international decisions and cease its enrichment activities and its construction of reactors," Levy said.

The United States, Israel and some other Western countries fear Iran's nuclear is aimed at produce atomic weapons. Iran says it wants nuclear power solely for energy production.

UK: Concerns remain

Earlier Saturday, Iran's hard-line President Mahmoud Ahmadinejad promised a global response if his country is attacked.

"Our options will have no limits... They will touch the entire planet," he said.

Also on Saturday, US State Department spokesman Darby Holladay said the reactor "underscores that Iran does not need an indigenous enrichment capability if its intentions are purely peaceful."

"We recognize that the Bushehr reactor is designed to provide civilian nuclear power and do not view it as a proliferation risk," Holladay said.

Meanwhile, Britain acknowledged Iran's right to build nuclear power stations, but warned that concerns remain about the Islamic republic's atomic program.

"We have always respected Iran's right to develop an exclusively civil nuclear power program," Foreign Office minister Alistair Burt said, as engineers began loading fuel into Iran's Russian-built Bushehr plant.

"The problem is Iran's continued refusal to satisfy the IAEA (International Atomic Energy Agency) and international community that its work on uranium enrichment and heavy water projects are exclusively peaceful."

AFP contributed to the report