The United States has urged Japan to consider imposing economic sanctions on Moscow if Russian troops invade Ukraine, diplomatic sources said Saturday.

Japan, however, has deferred its response to the U.S. request, fearing the possible ramifications on relations with Russia and bilateral issues, including a long-standing territorial dispute that Tokyo is seeking a breakthrough on, the sources said.

Japanese Prime Minister Fumio Kishida (R) speaks with U.S. President Joe Biden in a teleconference on Jan. 21, 2022, at his office in Tokyo. (Photo courtesy of Cabinet Public Relations Office)(Kyodo)

As tensions run high over a possible invasion amid a massive Russian military presence on the border of neighboring Ukraine, Washington hopes to rally Japan and other countries that uphold the rule of law in pressuring Moscow not to move in on Ukraine.

The United States and its European allies have warned that Russia would face "severe consequences," including economic and financial sanctions, if its troops were to invade Ukraine.

According to Japanese and U.S. diplomatic sources, Washington conveyed to Japan via diplomatic channels that it could not tolerate the movement of Russian troops and urged Tokyo to step up its criticism of Russia.

During a virtual summit with U.S President Joe Biden late last month, Japanese Prime Minister Fumio Kishida pledged to take "strong action in response to any attack" on Ukraine by Russia and continue close cooperation with the United States and other partners.

But Japan faces a balancing act of being in sync with the United States and other Western nations and trying not to ruffle Moscow's feathers to resolve the row over the sovereignty of a group of islands lying off Japan's northernmost main island of Hokkaido, the sources said.

The decades-old dispute over the Russian-held islands called the Northern Territories in Japan, and the Southern Kurils in Russia has prevented Tokyo and Moscow from concluding a postwar peace treaty.

Japan "would be compelled to take an appropriate measure in case of an invasion," a Japanese government source said. But there are calls within the government that it would be best not to announce the imposition of sanctions before an invasion takes place, unlike the United States and the European Union.

Kishida told parliament last month Japan is watching with "grave concern" Russia's military build-up near Ukraine's border and related developments, and that it will deal with the issue appropriately using the framework of the Group of Seven industrialized nations.

Following Russia's annexation of Crimea in 2014, Japan imposed sanctions on Russia, in line with moves by the United States and European nations.

But not wanting to aggravate relations with Russia in light of their territorial dispute, Japan's punitive measures, which included limiting imports of Crimea-made products, proved ineffective.

In Tokyo, Russian Ambassador to Japan Mikhail Galuzin warned at a recent press conference that Japan's plans to adopt sanctions against Russia, in line with those imposed on Moscow by some Western nations in the event of military aggression in Ukraine, would be "counterproductive."