Washington (CNN) President Donald Trump tweeted Saturday that 25 years of agreements with North Korea have failed, "making fools" of US negotiators.

Then he added cryptically that "only one thing will work."

In a pair of tweets sent Saturday afternoon, Trump said that past agreements with North Korea have all been violated.

"Presidents and their administrations have been talking to North Korea for 25 years, agreements made and massive amounts of money paid ... hasn't worked, agreements violated before the ink was dry, makings fools of U.S. negotiators," Trump wrote . "Sorry, but only one thing will work!"

Asked by reporters later Saturday about the cryptic tweet, Trump would only say: "You'll figure that out pretty soon."

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