America must massively boost its nuclear capability until the "world comes to its senses," President-elect Donald Trump said hours after a similar vow by Russia's Vladimir Putin. Trump made the statement on Twitter, without providing details or context, a day after meeting a group of Pentagon top brass, and shortly after Putin called for Russia to reinforce its own nuclear capabilities. "The United States must greatly strengthen and expand its nuclear capability until such time as the world comes to its senses regarding nukes," Trump tweeted. The open talk of ramping up nuclear capabilities — reminiscent of Cold War pledges — marks a jarring departure from the stance of President Barack Obama, who in a famous speech in Prague in 2009 called for the elimination of nuclear weapons. In 2010, Obama and Russia's then president Dmitry Medvedev signed the so-called New START treaty that calls for a significant reduction in the nuclear arsenals of both countries. Trump's remark came after Putin declared, "we need to strengthen the military potential of strategic nuclear forces," while boasting about the Russian army's performance in its Syria campaign. Russia's focus should be on "missile complexes that can reliably penetrate any existing and prospective missile defense systems," the Kremlin strongman added. A top Trump adviser tried to soften the impact of the tweet, saying the incoming president was not trying to change longstanding US positions on a global security issue. "What he's saying is he wants us to be ready to defend ourselves and he's not making new policy," Kellyanne Conway, who on Thursday was tapped as White House counselor, said in an interview with MSNBC. "I think all the president-elect is saying is that we have to be able to keep ourselves safe and secure and when others stop building their nuclear weapons, then we'll feel more secure in that regard," she explained, but sidestepped a question on whether Trump was referring to a specific actor posing new risks of proliferation.