TOKYO, June 13 -- Japan has quietly reopened high-level channels to Moscow, sending officials and business leaders to the Russian capital and returning to Russian oil, a pragmatic drift that has unsettled its G7 partners on the eve of a summit built around keeping Russia isolated.

The friction will follow Prime Minister Sanae Takaichi to France, where G7 leaders convene on June 15, with several European governments having already pressed Tokyo over contacts they fear send the wrong message while the West works to choke off the Kremlin's revenues.

The most pointed signal came in late May, when senior officials from Japan's foreign and trade ministries, accompanied by executives from the Japan Business Federation, spent two days in Moscow...