Oil major BP will sign a deal worth around $20 billion later on Tuesday to supply China National Offshore Oil Corp (CNOOC) with liquefied natural gas (LNG), BP Chief Executive Bob Dudley said at a conference in Moscow.

Dudley said the agreement between the two companies would be signed in London, as British Prime Minister David Cameron is due to announce a series of trade deals to coincide with the arrival of the Chinese Premier Li Keqiang for a three-day visit.

"It is a 20-year supply agreement on LNG. It is a fair price for them and a fair price for us. It is a good bridge between the UK and China in terms of trade," Dudley said.

BP already supplies CNOOC with LNG from Indonesia.