Gas imported from the US is to heat as many as 1.8 million UK homes after Centrica unveiled a supply deal worth £10bn.
The British Gas owner said the 20-year contract for commercial deliveries from the Sabine Pass liquefaction plant in Louisiana would play an important role in ensuring the UK's energy security.
However with gas reserves currently strained by Britain's prolonged winter, the bad news is that the first shipments are not due until September 2018.
The deal with Cheniere Energy Partners for 89 billion cubic feet of annual liquefied natural gas (LNG) volumes is the first time that the UK has entered into a formal gas import agreement with the United States.
In 2011, Centrica entered into a three-year supply agreement with Qatargas and a new 10-year contract to pipe gas to the UK from Norway from 2015.
The deal is enough to meet the annual gas demand of around 1.8 million UK homes.
Centrica chief executive Sam Laidlaw said: "This landmark agreement represents a significant step forward in our strategy, enabling Centrica to strengthen its position along the gas value chain and helping to ensure the UK's future energy security."
Prime Minister David Cameron added: "I warmly welcome this commercial agreement between Centrica and Cheniere.
"Future gas supplies from the US will help diversify our energy mix and provide British consumers with a new long-term, secure and affordable source of fuel."