Iceland's volcanoes could heat British homes within 10 years via the world's longest subsea power cable under plans to be announced by Prime Minister David Cameron on Thursday.

Cameron and Icelandic Prime Minister Sigmundur David Gunnlaugsson are expected to agree on setting up a U.K.-Iceland task force to assess the possible installation of the interconnector and the start of energy trading between the two countries, a note from Cameron's office said.

At around 1,200 kilometers, it would the longest subsea power interconnector and take seven to 10 years to build, it said.

"It would provide a sustainable, long-term renewable energy supply and increase the U.K.'s energy security," the note said.

The two countries first raised the idea in 2012 but scant progress has been made since.

The new task force is expected to report its findings within six months.

Britain is keen to increase its electricity import capacity due to a looming supply crunch in its domestic power generation.

Around 95 percent of Iceland's electricity comes from renewable sources such as hydro-electric plants and geothermal power from volcanoes.