TEHRAN, Iran (AP) — Iran's first nuclear power plant stepped up operations Monday after more than a decade of delays, pumping out electricity at up to 40 percent capacity and marking a major step forward in the Islamic Republic's nuclear program.

The Bushehr nuclear plant — which officials say could begin full-power operations in December — is also a cornerstone of Iran's drive to become a technological leader among Muslim nations with efforts such as a space program and long-range missile development.

The U.S. and its allies accuse Iran of using its civilian nuclear program as a cover to develop nuclear weapons. Iran denies the claim and says it only seeks reactors for energy and scientific research.

Senior Iranian and Russian officials attended celebrations for the official launch of the 1000-megawatt Bushehr plant on the Gulf. It began to generate between 350 to 400 megawatts of electricity, equal to 35 to 40 percent of the reactor's full capacity.

The Russian-built plant was connected to the national power grid for a test run Sept. 4, generating 60 megawatts.