TEHRAN, Iran — Iran claimed today that it has taken two major steps toward mastering the production of nuclear fuel, a defiant move in response to increasingly tough Western sanctions over its controversial nuclear program.

President Mahmoud Ahmadinejad oversaw the insertion of the first Iranian-made fuel rod into a research reactor in northern Tehran, the country’s official IRNA news agency reported.

Separately, the semiofficial Fars agency reported that a “new generation of Iranian centrifuges” had been installed and had gone into operation at the country’s main uranium enrichment facility at Natanz in central Iran.

The West suspects Iran’s nuclear program is aimed at producing atomic weapons, a charge Tehran denies, insisting it’s geared for peaceful purposes only, such as energy production.

The crisis has already resulted in sanctions placed on Iran’s economy, and there are fears that it could escalate to military action.

Iran’s nuclear announcements came as the country said today it halted oil exports to six European countries — the Netherlands, Spain, Italy, France, Greece and Portugal — in response to recent new European Union sanctions.

Iran has said it is forced to manufacture nuclear fuel rods, which provide fuel for reactors, on its own since international sanctions ban it from buying them on foreign markets. In January, Iran said it had produced its first such fuel rod.

IRNA boasted that the nuclear fuel announcement is the final step in the entire cycle of nuclear fuel — from extracting uranium ore to producing the finished rods.

Fuel rods are tube metals containing pellets made of low-enriched uranium. The rod is then inserted into a fuel assembly, which then is placed in the core of the reactor.

IRNA said the nuclear fuel rods were produced at Iran’s nuclear fuel fabrication plant in Isfahan, central Iran.

The centrifuges that Iran claims to be now manufacturing are machines that are used to enrich uranium. Low-enriched uranium — at around 3.5 percent — can be used to fuel a reactor to generate electricity, which Iran says is the intention of its program. But if uranium is further enriched to around 90 percent purity, it can be used to develop a nuclear warhead.

Iran has been producing uranium enriched up to 5 percent for years, and began enriching up to near 20 percent, considered a threshold between low and high enriched uranium — in February 2010.

Iran claims it needs the higher enriched uranium to produce fuel for the Tehran reactor that makes medical radioisotopes needed for cancer patients.

Israel is worried Iran could be on the brink of achieving nuclear weapons capability) and many Israeli officials believe sanctions only give Tehran time to move its nuclear program underground, out of reach of Israeli military strikes. The U.S. and its allies argue that Israel should hold off on any military strike on Iranian nuclear facilities to allow more time for sanctions to work.