Israeli officials said on Friday that a new United Nations report adds credibility to their warnings about Iran, as tensions grow between the Jewish state and its allies over how to tackle Tehran's suspect nuclear program.

The report by the U.N. nuclear agency, which emerged on Thursday, concluded that Iran had stepped up the installation of centrifuges capable of making weapons-grade material in an underground bunker at its Fordo underground facility, safe from most aerial attacks.

The U.N. report also said Iran has effectively shut down inspections of a separate site — the Parchin military complex — suspected of being used for nuclear weapons-related experiments, by shrouding it from spy satellite view with a covering.

It drew rapid criticism from Iranian Foreign Minister Ali Akbar Salehi, who said Friday the assertion about Parchin "does not make any technical sense." Iran denies the West's claims that it is seeking to develop weapons but its government makes no secret that it sees expansion of its nuclear program as a right.

An Israeli official said that the U.N report "confirms what Prime Minister (Benjamin) Netanyahu has been talking about for years now, that the Iranian nuclear program is designed to achieve a nuclear weapon." He spoke on condition of anonymity because he was not authorized to speak to reporters.

Israel has been weighing unilateral military action against Iranian nuclear facilities amid faltering international efforts to persuade Tehran to scale back its uranium enrichment, a process that would be key to bomb-making.

The United States opposes Israeli strikes. The strain between Washington and its longtime Israeli ally has been on full display this month, with a top U.S. military officer, Gen. Martin Dempsey, twice speaking out against a go-it-alone strike. He was quoted on Thursday as saying he would "not want to be complicit" in such an assault.

Washington worries that a premature Israeli attack could send global oil prices soaring and touch off a broad conflict possibly drawing in U.S. forces.

Many Israeli officials see U.S. reluctance as linked to the strength of American airpower, which can successfully hit more difficult targets and gives Washington a greater window for action.

But given Israel's more limited military means, the U.N. report could reinforce the view there that time for it to act independently is quickly running out, as key elements of Iran's nuclear program may soon be impervious to airstrikes from Israel's own aircraft.

Israeli leaders have said repeatedly that their country reserves the right to act on its own and will not leave what it sees as an essential security issue in the hands of others, even a powerful ally like the U.S. Israel considers Iran to be its most formidable enemy, given its nuclear program, its repeated calls for Israel's destruction and its proxy militant groups based near Israel's borders.

The U.N. says Iran has installed 1,000 centrifuges at the Fordo site since May, doubling the number there.

Israeli defense officials said Friday that they were surprised by the pace of the increase, but said the information contained in the U.N. report would not influence the country's decision whether to attack and if so, when. They also spoke on condition of anonymity because they were not authorized to discuss confidential assessments of the Iranian program.

Some nuclear experts have cautioned against concluding too much from the increase. Senior diplomats outside Israel familiar with the report said it was unclear how many of the centrifuges are operational. They also said it was unclear whether the machines would be used to produce reactor fuel or warhead-capable material.

In his comments to the official news agency IRNA on Friday, Iran's Salehi said the report wrongly accused his country of trying to clean up traces of nuclear experiments at the Parchin base even though removing radioactive residue would be impossible.

"Whoever has expertise in this field understands that these are offering excuses," he said. "Such issues cannot be eradicated through cleaning."

U.N. officials however have said they never expected to find radioactive residue at Parchin and were looking for other signs of testing.

Iranian state television said Friday that a summit of the 120-member Nonaligned Movement in Tehran supported its right to the peaceful use of nuclear energy. But it was not immediately clear whether the text of the conference's final declaration backed Iran's claims that its nuclear program is solely for those peaceful purposes, or simply asserted a general right to produce nuclear energy. Tehran had been hoping to use the summit to show that it is not isolated diplomatically.

Before leaving the conference, U.N. Secretary-General Ban Ki-moon told reporters that, as the head of the movement for the next three years, Iran has "a very important opportunity ... not only (to) raise their political profile in the international community, but also (to) demonstrate their leadership to exercise a moderate and constructive role in regional and international issues."

"I have urged the government of Iran to take concrete steps to build international confidence in the exclusively peaceful nature of its nuclear program," he said.


AP writers Geir Moulson in Berlin and Edith M. Lederer at the United Nations contributed to this report.