Russia's energy giant Gazprom said Wednesday it will start welding seams of its major pipeline for gas supplies to China in August.

"We have a clear action plan. We have distributed all duties and we have set tough deadlines," Gazprom said in a statement, citing company CEO Alexei Miller.

"Our goal is to weld Power of Siberia's first joint as soon as August," the Itar-Tass news agency quoted Miller as saying.

China and Russia signed the China and Russia Purchase and Sales Contract on East Route Gas Project and a memorandum on May 21, and the 30-year contract will see the east route pipeline starting providing China with 38 billion cubic meters of natural gas annually from 2018.

Also on Wednesday, vice president of Gazprom Alexander Medvedev said the company and China National Petroleum Corporation (CNPC) have inked a 25-billion-U.S. dollar advance payment agreement for gas supply.

He said Gazprom will also carry out further negotiations with CNPC on the gas supply of west line and the supply of liquefied natural gas (LNG) in near term.