Tehran ? Iran began the process of loading 163 fuel rods into the reactor core of its first nuclear power plant on Tuesday, celebrating the achievement as proof that Tehran can outmaneuver international sanctions.

The plant, built with Russian help in the southern port city of Bushehr, is not among the aspects of Iran’s nuclear program that are of top concern to the international community and is not directly subject to sanctions. It has international approval and is supervised by the U.N.’s nuclear monitoring agency.

Nevertheless, Iran has touted its startup as an act of defiance in the face of the penalties and has held up the plant as evidence that it only has peaceful nuclear intentions. The United States and some of its allies believe Bushehr and Iran’s other civil nuclear work is providing cover for a secret weapons program under development.

“The great Iranian nation can manage the sanctions with its resistance, efforts and endeavors and this is its proof,” Vice President Ali Akbar Salehi told a news conference broadcast on state TV.

The U.N. Security Council has slapped four rounds of sanctions against Iran over a separate track of its nuclear program — its enrichment of uranium, which can be a gateway to developing atomic weapons.

Iran denies such an intention and says it only seeks to master the technology to produce fuel for a planned network of nuclear power facilities, starting with Bushehr.

On Tuesday, Iran loaded the first three fuel assemblies into the plant’s reactor core, beginning a process that will take two months.