TEHRAN, Iran - Iran has boosted its supply and output of reactor-grade nuclear material significantly, according to a quarterly report issued yesterday by the United Nations' arms-control division.

In Syria, international inspectors reported finding unexplained particles of modified uranium at a lab in Damascus, far from the site of an alleged nuclear site.

The inspectors said they discovered the artificially modified uranium particles in samples taken last year from a facility called Miniature Neutron Source Reactor in the Syrian capital. The report disclosed few other details about the discovery or Syria's response to the International Atomic Energy Agency's request for an explanation.

The uranium particles "are of a type not included in Syria's declared inventory of nuclear material," it said.

The reports by the IAEA came a day after President Obama called on Iran and other nations to avert a Mideast nuclear-arms race and strive for a world without atomic weapons.

The United States and the West allege that Iran is violating the spirit of the Nuclear Non-Proliferation Treaty by using a civilian nuclear energy program as a cover for developing the means to produce atomic weapons. Iranian leaders deny the charge.

Iran's nuclear research program also has become a campaign issue ahead of the country's presidential election next Friday. President Mahmoud Ahmadinejad has touted the program as a point of national pride, even adding the symbol of the atom to his campaign posters, while his challengers say he has isolated Iran with his tough talk and uncompromising stance.

Arms-control experts say the IAEA findings suggest Iran continues to master the enrichment process without running into any major glitches.

"Iran's nuclear program comes across to me as if Iran has its head down and burrowing forward," said Jacqueline Shire at the Institute for Science and International Security, a Washington-area think tank. "It's not stopping."

The dryly worded reports, delivered to the governing board of the agency and obtained by the Los Angeles Times, said Iran increased its supply of low-enriched uranium in the last three months by 30 percent, to nearly 3,000 pounds, and feeds uranium gas into about 5,000 high-speed centrifuges, up 25 percent since February, the time of the last report. It also has 2,000 more centrifuges spinning in preparation for being fed uranium gas to turn into nuclear material.

Scientists say 3,000 pounds of low-enriched, or reactor-grade, uranium of the type Iran has would be more than enough to build a single nuclear weapon if Iran were to boot international inspectors, renege on treaty obligations, and further refine its supplies.