FTSE 100-listed Centrica has signed a four-year, multi-billion pound gas deal with Qatargas, it announced Wednesday. The agreement, under which it will purchase up to 3m tonnes a year of liquefied natural gas (LNG), builds on an existing agreement that was signed in early 2011. The British Gas-owner said the extension could see it provide gas to meet approximately 13% per cent of UK annual residential gas demand, enough to meet the needs of around 3m households.Centrica Chief Executive, Sam Laidlaw said: "We are delighted that we continue to deepen our relationship with Qatargas and continue to build our LNG business by integrating our positions along the gas value chain. "It is vital that the UK has a diverse range of sources of supply to meet its energy requirements. In a competitive international market, contracts like this underpin the UK's access to global LNG supplies for the benefit of customers."The previous deal comes to an end in June 2014, and so the extension secures important gas supplies for Centrica, it said. "Long term deals of this kind with reliable suppliers like Qatar are vital for our future energy security," Energy Minister Michael Fallon said.NR