TOKYO, April 28 -- Japanese Prime Minister Shinzo Abe has declined an invitation from Russia to attend events to be held in Moscow to commemorate the 70th anniversary of the victory over Nazi Germany and the end of World War II in Europe, government officials confirmed Tuesday.

Chief Cabinet Secretary Yoshihide Suga, Abe's top spokesperson, said that Japan's Ambassador to Russia Chikahito Harada will attend the events on May 9 in Moscow in the prime minister's absence, as according to his officials, his current trip to the United States has created a tight schedule.

"Prime Minister Abe has been invited to the ceremony, but he will skip it due to his schedule," Suga said, adding that the Japanese leader will also be busy with parliament here and related affairs once his eight-day tour to the U.S. concludes.

Suga quashed notions that Abe's declining Moscow's invitation was connected to the Group of Seven (G7) nations' denouncing and slapping sanctions on Russia due to its actions over Ukraine.

But sources close to Abe said Tuesday that the prime minister had "considered various factors in making his decision, including his personal relationship with Russian President Vladimir Putin."

They suggested in contrast to Suga's remarks that Abe was following suit with the United States and other western countries to not take part in the commemorative WWII events in Moscow due to their disputes with Russia over the Ukraine crisis.

Suga said however that Japan was working hard to fulfill its commitment to a planned visit to Japan by Putin this year, although noting that "nothing had been decided yet."

Tokyo is keen to resolve an ongoing territorial dispute with Moscow and some sources have suggested that Abe's declining could possibly further strain ties in this regard.

The territorial dispute has been rumbling on for decades and has prevented the two sides from signing an official peace treaty.

With rising tensions and conflicts concerning Ukraine, Abe doesn't want to alienate Putin by following the U.S. and other countries, but at the same time is cognizant of Japan's relationship with other G7 members.

Observers have suggested that in light of Abe's refusal and previous sanctions levied on Russia, Putin's visiting Japan this year was now far from a done deal and could adversely affect the ongoing, territorial impasse between the two sides.