U.S. President-elect Donald Trump tweeted Thursday that “The United States must greatly strengthen and expand its nuclear capabilities until such time as the world comes to its senses regarding nukes.”

His team has been trying to clarify what could be seen as an alarming statement from the on bolstering the country’s nuclear capabilities.

Donald Trump gave no context or details of what he meant.

On Friday morning, MSNBC reported that Trump told the network ““Let it be an arms race. We will outmatch them at every pass and outlast them all.”

Trump press secretary Sean Spicer, speaking after “Donald Trump’s remakers, said there would be no arms race “because other countries would come to their senses.”

Russian President Vladimir Putin told reporters Friday in his annual year-ending news conference that he sees nothing unusual in Trump’s pledge to strengthen U.S. nuclear forces, nothing the president-elect had said as much in his campaign speeches.

Vladimir Putin said, while the U.S. has a bigger military, he did not see the Americans as a potential aggressor, and that Russia’s focus should be on missiles that can penetrate any existing nuclear defense systems.

U.S. State Department spokesman John Kirby said Thursday the Obama administration has been “trying to get us on a path to a world without nuclear weapons. First, by reducing our stockpile and our launchers…Number two, diminishing the role of nuclear weapons in our security strategy and number three, securing the Iran deal.”

Trump transition spokesman Jason Miller says Trump was talking about the need to keep nuclear weapons away from terrorists and dangerous world leaders.

“President-elect Trump was referring to the threat of nuclear proliferation and the critical need to prevent it, particularly to and among terrorist organizations and unstable rogue regimes,” Miller said.

Trump issued his tweet about the same time Russian President Vladimir Putin told his defense team Russia needs to “strengthen the military potential of strategic nuclear forces,” including “missile complexes that can reliably penetrate any existing and prospective missile defense systems.”

Russia has said a U.S. missile defense system in Eastern Europe is a threat, while the U.S. says it is aimed at countering a possible missile launch from Iran.

U.S. arms control experts say the U.S. and Russia possess roughly the same number of weapons in their nuclear arsenals — more than 7,000 each.

Trump said during the campaign that modernizing the U.S. nuclear arsenal is necessary “to ensure it continues to be an effective deterrent.”

But if he decides to expand it, it would be a sharp reversal of more than 50 years of U.S. policy which has focused on cutting its nuclear stockpile.

The U.S. and Russia signed a major weapons deal in 2010 limiting the number of nuclear warheads and missile launchers each side can have.

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