Japan's Mitsui & Co is close to buying a stake in the second phase of QatarEnergy's massive North Field project as it seeks to secure stable liquefied natural gas (LNG) supply, five sources close to the matter told Reuters.

If reached, the deal would bolster Japan's energy security as it looks to meet an increase in electricity demand from the artificial intelligence boom with conventional fuels, since adoption of renewable power is slowed by delays at wind power projects.

Set to become the world's largest, The North Field LNG project, is expected to boost QatarEnergy's output of the super-chilled fuel by about 64% to 126 million metric tons per annum by 2027, from 77 mtpa now, said the report.

Of that, the second phase, called North Field South, will add 16 mtpa at a cost of about $17.5 billion, according to a 2024 research report by the Japan Organization for Metals and Energy Security, it added.

QatarEnergy holds a 75% stake in North Field South while majors TotalEnergies and Shell hold 9.375% each and ConocoPhillips has a 6.25% stake.

QatarEnergy did not respond to a request for comment and Mitsui declined to comment.

The sources spoke on condition of anonymity as the matter is not yet public. The size of the stake and its value were not immediately available.

"Talks are at an advanced stage," said one of the sources.

Another industry source said Mitsui and QatarEnergy are finalising terms.

One of the sources said Malaysia's Petronas has also expressed interest in an equity stake in the project, without giving further details.