A senior U.S. diplomat cautioned Japan on Thursday against seeking closer ties with Russia, given that both Washington and Tokyo have imposed sanctions on the country over its annexation last year of Crimea, southern Ukraine.

Daniel Russel, assistant secretary of state, told a news conference in Washington that he was confident that the Abe government is "committed to the principle of not pursuing business as usual (with Russia) under the current circumstances."

Prime Minister Shinzo Abe had told U.S. President Barack Obama during their summit last month he might try to invite Russian President Vladimir Putin to Japan later this year, according to government sources in Tokyo.