Officials already had told the AP yesterday 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.
Today, two diplomats said the boycott applied to the 2016 meeting as well. They cited as their source a diplomatic note from Moscow to the US and other nations planning to participate. The diplomats spoke on condition of anonymity because they are not allowed to discuss confidential information.
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-US tensions over Ukraine added to the Kremlin's decision to stay away.
More From This Section
At the last summit, 35 countries discussed turning international guidelines on nuclear security into national laws and opening their procedures for protecting nuclear installations to independent scrutiny. The summit also featured new reduction commitments, with Japan, Italy and Belgium agreeing to cut their stocks of highly enriched uranium and plutonium.
But Russian reluctance to go along with the U.S.-backed initiative already was apparent. Moscow refused to back such a 35-nation agreement, as did China, India and Pakistan. All four of those nations have nuclear weapons.
Outlining his vision in a keynote speech five years ago, Obama announced a new effort to secure sensitive nuclear material within four years and to cripple black-market trade.