The United Nations' nuclear watchdog says Iran has doubled the number of centrifuges for enriching uranium.

According to the International Atomic Energy Agency's latest quarterly report, Iran has also "significantly hampered" the agency's ability to inspect the Parchin military site through "extensive activities" to "sanitize" evidence of possible nuclear explosion tests.

Iran has now installed 75% of the machines needed to complete its underground site near the holy city of Qom to process nuclear fuel, possibly for weapons, The New York Times says.

The news comes as Israel has increased pressure on President Obama to attack the site, suggesting that it will if he won't. The Times writes, "With senior Obama administration officials warning Prime Minister Benjamin Netanyahu and his cabinet that a military strike on Iran's nuclear sites would be counterproductive, the report offers arguments for both sides in the debate."

The IAEA's latest report says Iran now has 2,140 centrifuges in the underground Fordo complex in mountains near Qom. In its May report, the agency says, there were 1,064, adding that the new machines are not yet operating.

Since May, the report states, Iran has produced an additional 45 kilograms of enriched uranium, bringing its total since 2010 to nearly 190 kilos (418 pounds). Reuters notes that "a large part of that had been earmarked for conversion to reactor fuel. Refined uranium can have both civilian or military uses, depending on the enrichment level."

Iran says Fordo will be used to enrich uranium to a maximum concentration of 20% for civilian use, including a medical research reactor. In May, U.N. inspectors found traces of uranium enriched at 27%, closer to weapons-grade material. Iran said those readings could be accidental.

At the Parchin site, east of Tehran, the IAEA report states, "Significant ground scraping and landscaping have been undertaken over an extensive area at and around the location," noting that five buildings had been demolished and power lines, fences and paved roads eliminated.

"The activities observed ... further strengthen the agency's assessment that it is necessary to have access to the location at Parchin without further delay", the IAEA said.

The White House said it was "closely studying" the report.

"We are closely studying the details of the report, but broadly speaking it is not surprising that Iran is continuing to violate its obligations," White House press secretary Jay Carney told reporters, the Israeli newspaper Haaretz says. "As the report illustrates, we are in a position to closely observe Iran's program."

"The president has made clear frequently that he is determined to prevent Iran from obtaining a nuclear weapon," Carney said. "So long as the Iranian regime refuses to comply with its international obligations, the United States, with its allies, will continue to take actions to further isolate and penalize Iran and the regime."

The chairman of the Joint Chiefs of Staff, Gen. Martin Dempsey, told reporters in London today that an Israeli attack on Iran would delay but not stop its nuclear program.

"I don't want to be complicit if they (Israel) choose to do it," Dempsey said, The Guardian reported earlier.

In Iran, Ayatollah Ali Khamenei, the country's supreme leader, reiterated his assertion that nuclear weapons were a "big and unforgivable sin" and contrary to Islam.

"I declare that the Islamic Republic of Iran has never been after nuclear weapons and it will never abandon its right for peaceful use of nuclear energy," Khamenei told delegates at a gathering of non-aligned nations in Tehran, The Washington Post says.

He added, however, that Iran would never yield to Western pressure.

See how the official Islamic Republic News Agency reported the IAEA report, along with the official FARS news agency's coverage of the meeting of the Non-Aligned Movement.