Japan's government warned on July 1 that its "interests must not be undermined" after a Moscow decree ordered a transfer of the operations of a multibillion-dollar joint oil and gas project to a new Russian entity.
The decree over control of the Sakhalin-2 project in Russia's Far East was signed by Russian President Vladimir Putin a day earlier and could mark a dangerous new precedent in Moscow's relations with foreign investors.
"Speaking generally, we believe our resource interests must not be undermined," Japanese government spokesman Seiji Kihara said. He said Tokyo was "closely examining the impact on liquefied natural gas (LNG) imports."
Japan relies heavily on LNG imports and had previously ruled out Japanese companies' withdrawal from the Sakhalin-2 project despite Tokyo's support for international energy sanctions on Russia over its invasion of Ukraine.
Prime Minister Fumio Kishida said later that his government did not think the decree "will immediately stop LNG imports," but his economy minister said officials were examining other potential suppliers.
Industry Minister Koichi Hagiuda told reporters that Japanese officials do not regard the decree as a requisition but interpret it as Putin asking stakeholders about a possible handover to a new company.
Japanese trading houses Mitsui and Mitsubishi Corp own a combined 22.5 percent in Sakhalin-2.
Russian officials have been stung by massive financial and other sanctions since tens of thousands of Putin's troops rolled across Ukraine's borders on February 24.
Putin's decree reportedly creates a new Russian operator of Sakhalin-2 and requires current owners to apply to Moscow for the right to participate in it.
Asked about Sakhalin-2 as an example of what might happen to other joint projects with Western investors, Kremlin spokesman Dmitry Peskov said Russia would act on a case-by-case basis.