Beijing  - US firm First Solar Inc said it signed a framework agreement with the Chinese government Tuesday to build what could become the world's largest solar power plant in China's Inner Mongolia region.

Arizona-based First Solar said Tuesday's deal, following an initial agreement in September, marked "another critical step towards the realization of the world's largest solar power plant."

The agreement between First Solar and the government of Inner Mongolia's Ordos city gives more details of the project and specifies local support for developing the 2-gigawatt solar plant.

Construction is scheduled to start in June on the 30-megawatt initial demonstration phase, the US firm said.

The agreement marks a "critical step forward in the approval process for the Ordos project, one of the world's most ambitious renewable energy projects," First Solar chief executive officer Rob Gillette said in a statement.

"Solar energy will play a significant role in achieving China's low carbon future," Yun Guangzhong, the mayor of Ordos city, was quoted as saying.

"We are very pleased to be partnering with one of the solar industry's global leaders in a project of such significance," Yun said.

The signing ceremony took place during US President Barack Obama's first visit to China, which produced several cooperation agreements on clean energy.

First Solar said final agreement on the Ordos plant remained "subject to the negotiation and execution of definitive agreements among the parties."

The plant would be completed over 10 years, the US company said in an earlier statement.

Phases 2, 3 and 4 were scheduled to add 100 megawatts, 870 megawatts and 1,000 megawatts with completion in 2014 for the first two and 2019 for the final phase.

China had guaranteed the long-term pricing of electricity from the plant through a feed-in tariff which would be "critical to this project," First Solar said in September.(dpa)