BP is set to sign a deal later on Tuesday to supply China National Oil Corporation (CNOOC) with liquefied natural gas (LNG).Chief Executive Bob Dudley said the agreement, which is worth around $20bn, would be signed in London.It comes as UK 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 at a conference in Moscow, according to Reuters.BP currently supplies CNOOC with LNG from Indonesia.RD