On Dec. 22, President-elect Donald Trump startled the worldwide community of arms-control experts with a message on Twitter.

He wrote, “The United States must greatly strengthen and expand its nuclear capability until such time as the world comes to its senses regarding nukes.”

The next day, Trump spoke off-camera with Mika Brzezinski of MSNBC’s “Morning Joe” program and reportedly told her, “Let it be an arms race. We will outmatch them at every pass and outlast them all.”

But on the same day, President Obama signed legislation that could do more to set off an arms race than anything the president-elect has said. The National Defense Authorization Act, an annual bill affecting every aspect of the U.S. military, for the first time strikes the word “limited” from the language that describes the nation’s missile defense system.

Another provision in the law calls for the Pentagon to begin research, development and testing of space-based missile defenses.

That opens the door for virtually unlimited spending on new missile defense systems aimed at countering a nuclear threat from Russia and China, an escalation from current systems designed to stop smaller threats from nations like North Korea.

This significant change in U.S. policy was made quietly on Capitol Hill and approved by overwhelming bipartisan majorities in both houses of Congress. Although President Obama issued a four-page signing statement criticizing parts of the bill, he was silent on the changes in the nuclear defense policy.

A 2012 study of missile defense technologies conducted by a panel of the National Academy of Sciences at the request of Congress estimated the minimum cost of building a space-based missile defense system at $200 billion, not including hundreds of billions of dollars to operate it. The co-chair of the panel, retired Lockheed Corp. executive L. David Montague, said in an interview that a missile defense system could never ensure against a dedicated attack, but was “an opportunity to waste a prodigious amount of money.”

Of course, to some members of Congress, it’s not a waste of money if it creates a brand-new defense facility and high-paying jobs in their districts.

But the new arms race is not solely of U.S. making. Trump’s message on Twitter followed a speech by Russian President Vladimir Putin vowing to “strengthen the strategic nuclear forces” of his nation, and calling for an upgrade of non-nuclear forces so they are “capable of neutralizing any military threats.”

The Washington Post’s Bob Woodward reported that military and intelligence sources see “a giant buildup” of Russia’s nuclear arsenal while the United States relies on aging weapons from the Kennedy and Reagan eras. Trump’s national security adviser, retired Lt. Gen. Michael Flynn, told Woodward the president-elect is convinced the United States has to modernize and spend “vast amounts of money” to maintain a position of strength.

The so-called “peace dividend” that followed the end of the Cold War in the 1990s appears to have run its course. The U.S. is headed for a major expansion of military spending, set in motion by lawmakers of both political parties, a president and a president-elect.

The biggest fight may be between Congress and the White House about where the money will be spent first.