"Nothing has changed in the seven months since he took office. The U.S. nuclear arsenal is no more or no less powerful." Kingston Reif director of disarmament and threat reduction policy at the Arms Control Association

Shortly after his inauguration, Trump ordered a comprehensive review of the U.S. military, including conducting a Nuclear Posture Review. That review began in April and is scheduled to be completed by the end of the year. Any improvements that the Trump administration seeks to make to the U.S. nuclear capability will result from that review, said Kingston Reif, director of disarmament and threat reduction policy at the Arms Control Association. "Nothing has changed in the seven months since he took office. The U.S. nuclear arsenal is no more or no less powerful," he told CNBC. Other nonproliferation experts and defense reporters also expressed doubt over the president's claim.

"Any decision that the president were to make now, or that he took in January, would take years to implement," Jon Wolfsthal, former National Security Council senior director for nonproliferation and arms control under Obama, told The Washington Post. "I'm very skeptical of the idea that Trump believes that he has modernized or adjusted our arsenal because there have been no visible changes to it." Aaron Mehta, senior Pentagon correspondent for Defense News tweeted, " ... no, the president has not done a single thing to the nuclear stockpile that wasn't already underway."

Modernization was already underway

The Obama administration completed the last Nuclear Posture Review in 2010 and implemented many of the current efforts to modernize the arsenal. The modernization effort includes updating, rebuilding and developing intercontinental ballistic missiles, bombers and submarines that make up the U.S. strategic delivery system and would facilitate a nuclear strike. Despite the Obama administration committing to renewing this so-called nuclear triad, these programs will not reach completion for a decade or more, according to Reif at the Arms Control Association. "These are all in their infancy. These are acquisition programs that are going to take 10, 15, even 20 years to complete. The majority of them aren't going to enter service until the mid-2020s," he said.