Cooperation between China and Russia in the energy sector has brought tangible benefits to both countries and is expected to yield further positive results, says Li Hui, China's ambassador to Russia.

"Energy cooperation is a crucial part of bilateral practical cooperation and testifies to the high-level China-Russia comprehensive strategic partnership," Li told Xinhua News Agency ahead of Vice-Premier Zhang Gaoli's visit to Russia.

Zhang, who has completed his visit to Turkmenistan, will attend the 11th meeting of the China-Russia Energy Cooperation Committee and a groundbreaking ceremony for the China-Russia east-route gas project.

Li said the 10 meetings between the countries' vice-premiers in the past six years have injected impetus into the project, adding that bilateral energy cooperation is complementary and mutually beneficial.

"Energy cooperation is an important issue for discussion every time the heads of China and Russia meet, and it is also an essential part of all the communiques the two countries have inked through the years," said the ambassador.

In 2013, China imported 24.35 million metric tons of crude oil, 27.28 million tons of coal and 3.5 billion kWh of power from Russia, he added.

He said the first two reactors at the Tianwan nuclear power plant in Jiangsu province, a major joint project between the countries, are being tested, and the other two are under construction.

During Russian President Vladimir Putin's visit to China in May, the two sides signed a series of agreements on major projects such as a $400 billion natural gas contract and annual deliveries of 3 million tons of liquefied natural gas.

"In general, energy cooperation is in good condition, ... but problems do exist," said the ambassador.

"The main problem is that both sides have limited direct investment in the energy sector, which is incompatible with the scale of bilateral trade."