Up to 50 agreements on energy, finance, aerospace, railway and other fields are expected to be signed by China and Russia during Chinese Premier Li Keqiang's upcoming visit, said the Russian Ambassador to China on Friday.

The premier left Beijing on Thursday bound for Germany, Russia and Italy and will return on Oct.17.

Agreements and commercial contracts on energy, banking, railways and infrastructure will improve the already massive trade and investment ties between the two, said Ambassador Andrey Denisov.

In May, the two countries signed a 30-year gas deal during Russian President Vladimir Putin's trip to Shanghai, ending a decade of talks.

Progress is expected on the west route gas pipeline negotiations, Chinese Vice Foreign Minister Cheng Guoping said on Wednesday at a news briefing. On Thursday, the China National Petroleum Corp said the designs and construction plans for the east route gas pipeline had been approved.

The ambassador described Sino-Russia relations as at "the highest level ever", with the two neighbors expanding cooperation in various fields without any pending issues.

China has been Russia's largest trading partner for the past four years, with a bilateral trade of 89.2 billion US dollars in 2013. In the first half of the year, Sino-Russia trade reached 44.5 billion US dollars, up 3.3 percent.