Four government sources familiar with the plans said that Japanese officials are working on ways to get around restrictions on releasing national crude oil reserves in tandem with other large economies to lower prices.

While Prime Minister Fumio Kishida indicated his readiness over the weekend in response to a request from Washington, the world's fourth-largest oil buyer is limited in how it can use its reserves, which are made up of both private and public inventories and are normally only used in times of shortage.

As a legal workaround, one of the sources said the government was considering releasing a portion of the state-held stocks that was less than the minimum amount required. Officials are also considering private stocks held by the national reserve, which some advisers think can be released without restrictions, according to a second source. 

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Hirokazu Matsuno, the Chief Cabinet Secretary, said that nothing had been decided, while Kishida indicated on Saturday that the government was considering what it could do legally.

After members of OPEC and its allies consistently refused to speed up their production increases, the Biden administration made the unusual request to other large economies to consider releasing oil from their strategic reserves. 

Official sources said that Japan and the US will coordinate an announcement of the release of oil reserves as soon as this week.

According to official figures, Japan's oil reserve had 145 days' worth of daily petroleum use at the end of September, well above the legal requirement of 90 days. Private-sector reserves total 90 days, exceeding the minimum requirement of 70 days.