With the United States and Europe slapping additional sanctions on Russia over the downing of a commercial plane in Ukraine, there are growing views in Japan that a visit by Russian President Vladimir Putin to Tokyo this fall isn't going to happen, government sources said.

"As the international community views Russia more severely, it is difficult to think that the two governments can lay the groundwork in the coming three to four months for Mr. Putin's visit," a Foreign Ministry source said Friday. "It is difficult to realize the visit in the fall."

Prime Minister Shinzo Abe's government has attached great importance to Putin's visit as part of efforts to advance negotiations on reacquiring the four Russian-held islands off Hokkaido taken near the end of the war. The dispute has prevented Tokyo and Moscow from concluding a formal peace treaty.