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 possible ramifications on bilateral issues with Russia, including a long-standing territorial dispute that Tokyo is seeking a breakthrough on, the sources said.

With tensions running 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 invade.