The first independent assessment of Iran’s atomic program since the June presidential election shows Iranian officials steadily expanding the country’s nuclear capacity while also avoiding provocative steps that might trigger an Israeli military strike.

United Nations nuclear inspectors who visited Iranian nuclear facilities in the summer observed the installation of hundreds of new centrifuges in two different facilities the country uses to make enriched uranium. The officials also found that Iran’s available stockpile of low-enriched fuel has grown an additional 6 percent since May to more than 15,000 pounds, enough in theory for about nine nuclear bombs if the material is enriched to weapons-grade.

Iran, however, was seen converting more of its uranium stockpile to a metal form that cannot be easily used in a weapons program. In a pattern first observed last year, Iran appeared to be capping its stocks of the most weapons-sensitive forms of uranium at a level just shy of the “red line” set by Israeli officials last fall.

Despite the mixed report on Iran’s nuclear progress, the International Atomic Energy Agency slammed Tehran over its refusal to cooperate with the U.N. watchdog’s efforts to inspect sites where Western governments believe Iran carried out secret weapons research in the past.

“The agency is unable to provide credible assurance about the absence of undeclared nuclear material and activities in Iran, and therefore to conclude that all nuclear material in Iran is in peaceful activities,” stated the report, prepared for a meeting next month of the U.N. agency’s 35-nation­ board of governors.

The document will probably be closely studied as the first report card on Iran since the June presidential election that replaced Mahmoud Ahmadinejad with Hassan Rouhani, a cleric and a relative moderate within Iran’s leadership.

Although Rouhani’s inauguration on Aug. 4 came near the end of the IAEA’s reporting cycle, analysts are searching for early evidence of the new government’s intentions. Rouhani has pledged to pursue a more moderate foreign policy compared with his predecessor, and he has hinted at a willingness to accept nuclear concessions in return for relief from Western sanctions. But Rouhani also has vowed that Iran will not give up its right to what he says is a peaceful nuclear energy program.

Nuclear experts who reviewed the report said it offered little to assuage Western anxieties. With more than 15,000 centrifuges now installed at its main uranium facility, Iran is rapidly shrinking the time it would need to assemble an atomic bomb if it decides to launch a crash weapons program in secret, analysts said.

At the same time, the report reflects both cautiousness by Iranian leaders as well as continued technical difficulties. David Albright, a former U.N. nuclear inspector and president of the Institute for Science and International Security, said Iran appears to be struggling to make fuel plates for a new heavy water reactor that the United States fears could someday make plutonium for nuclear weapons. He also noted that Iran, for unknown reasons, appears to be stalling on bringing many of its new centrifuges into production.