Japan has repudiated a spur of the moment decision by Russian president Vladimir Putin to formally end World War II with a peace treaty "without any preconditions" and before the year ends because it would cede to Russia permanent control of several Japanese islands illegally seized by the Soviet Union.

Putin broached the idea to Japanese Prime Minister Shinzo Abe at the just ended Eastern Economic Forum in Vladivostok. This meeting has been held since 2015 under Putin's initiative. It's aimed at attracting investments to Russia's heavily underdeveloped Far East region, including the disputed Kuril Islands, which is the reason for Putin's proposal to Abe.

Abe didn't respond to Putin's sudden suggestion, even after the Russian leader said, "I was not joking."

The official Japanese response came a day later when chief cabinet secretary Yoshihide Suga officially rejected Putin's offer. Suga said while Abe and Putin had held frank talks at a number of summits, there is absolutely no change to Japan's perspective of resolving the problem of rights over the Northern Territories before signing a peace treaty.

At Vladivostok, Abe said that over the long stretch of more than 70 years since the end of World War II, Japan and Russia have yet to conclude a peace treaty between them. He noted that both he and Putin agree this is an abnormal state of affairs.

Abe and Putin have met 22 times over the Kuril Islands since Abe came into power in 2012. No significant progress has been made in resolving this thorny issue.

Political observers also pointed out that the suddenness of Putin's proposal might have been prompted by the need to prevent Japan from deploying a United States anti-ballistic missile defense system in northern Japan to counter a North Korea missile attack. This U.S. defense system could also be used to counter Russian missile attacks, as well.

The disputed islands are part of the Kuril Islands lying between Hokkaido in northern Japan and Russia's Sakhalin peninsula to the northeast. The Soviet Union invaded and seized the southern Kuril Islands held by Japan in mid-August 1945 towards the end of World War II.

These islands, called the Northern Territories or Southern Chishima by Japan, consist of four islands and islets, and are the reason why Japan and Russia have not signed a formal peace treaty ending World War 2. Japan wants Russia to relinquish control of the islands as a pre-condition to a peace treaty. Russia has said it would never do that.

The disputed islands (Etorofu Island, Kunashiri Island, Shikotan Island and the Habomai Islands) are under Russian administration as the South Kuril District of the Sakhalin Oblast. The Soviet Army evicted all the 17,000 Japanese inhabitants of the islands in 1946. The 20,000 residents of these islands today are Russians.

Putin's sudden decision to tell Abe he wanted to sign a peace treaty without preconditions means Japan will have to cede control over the Northern Territories to Russia permanently, as provided for by the Treaty of San Francisco of 1951 that formally ended American's occupation of Japan. The U.S., however, does not recognize Russia's sovereignty over the Kuril Islands.