A U.S. intelligence official says Russia "probably" is not adhering to a moratorium on nuclear weapons testing.

The statement was made Wednesday by the director of the Defense Intelligence Agency, Lt. Gen. Robert Ashley.

Speaking at the Hudson Institute, Ashley said Russia's nuclear activities would help it improve its weapons capabilities. He said the United States, by contrast, has foregone such benefits by adhering to a testing moratorium.

More broadly, Ashley asserted that Russian actions have "strained" key pillars of a network of international arms control agreements, including the Chemical Weapons Convention and the Open Skies Treaty.