Russian President Vladimir Putin answers journalists' questions during the annual big conference at the International Trade Center in Krasnaya Presnya, 20 December 2012 (RIA Novosti / Iliya Pitalev)

Russian President Vladimir Putin answers journalists’ questions during the annual big conference at the International Trade Center in Krasnaya Presnya, 20 December 2012 (RIA Novosti / Iliya Pitalev)

Russia has informed the United States that it will boycott the 2016 Nuclear Security Summit, diplomats told The Associated Press on Tuesday, potentially stripping the meeting of one of its key participants and hurting efforts initiated by President Barack Obama to reduce the threat of nuclear terrorism.

Officials already had told the AP on Monday that Moscow was absent from last week’s initial summit planning session in Washington but had left unclear whether Russia planned to attend the summit itself.

© Oliver Bunic/Bloomberg The boycott is ostensibly on account of the summit’s alleged political nature.On Tuesday, two diplomats said the boycott applied to the 2016 meeting as well. They cited as their source a diplomatic note from Moscow to the U.S. and other nations planning to participate. The diplomats spoke on condition of anonymity because they are not allowed to discuss confidential information.

One of the diplomats said the note expressed opposition to the summit because of its alleged political nature. He cited the note as saying that any meeting on nuclear security should be on a technical level and convened not by a nation but by the U.N.’s International Atomic Energy Agency.

Russia has participated in such summits in the past. But the diplomat, who is familiar with Moscow’s stance, said it already had reservations while attending the last meeting in March at The Hague. He did not specify but added that the “changed political atmosphere” — shorthand for Russia-U.S. tensions over Ukraine — added to the Kremlin’s decision to stay away.