China National Offshore Oil Corporation (CNOOC) announced late Tuesday that it had signed a 20-year deal with London-based oil giant BP for liquefied natural gas (LNG) supply.

According to the agreement, BP is to supply up to 1.5 million tonnes per annum (mtpa) of LNG from its global portfolio to CNOOC over 20 years starting in 2019, said CNOOC in a statement.

The parties expect to reach a full commercial contract in mid-2014, it added.

Under the witness of Chinese Premier Li Keqiang and British Prime Minister David Cameron, Mr. Wang Yilin, Chairman of CNOOC, and Mr. Dev Sanyal, EVP of BP, signed the agreement, it said.

"The agreement with BP will not only deepen the cooperation between both parties, but also further diversify the LNG supply of CNOOC," the statement quoted Wang as saying.

"CNOOC will continuously strive to acquire competitive natural gas resources around the world, and to make positive contribution to securing clean energy supply as well as protecting ecological environment of China," Wang added.

CNOOC and BP have built sound relationship throughout the LNG value chain since 2001. In its statement, CNOOC hailed the deal as a "new milestone" in the cooperation between the parties.

CNOOC imported more than 13 million tonnes of LNG, accounting for 72 percent of the country's total LNG import, in 2013.

By the end of May 2014, CNOOC had built and put six LNG receiving terminals into operation in Guangdong, Fujian, Shanghai, Zhejiang, Zhuhai and Tianjin respectively, with a total LNG receiving capacity of 24.8 mtpa.

Meanwhile, the Hainan, Shenzhen, Yuedong LNG receiving terminals are under construction and will be commissioned before the end of 2015, CNOOC said.

Also on Tuesday, CNOOC and another oil giant Shell signed a "global strategic cooperation agreement," vowing to push forward their partnership in China and the world and jointly explore more cooperation opportunities in the up, middle and down streams, according to the statement.