WASHINGTON -- Reaction to U.S. President Donald Trump's decision to cancel next month's summit with North Korea's Kim Jong Un:

--"The art of diplomacy is much harder than the art of the deal." Sen. Bob Menendez, D-NJ

-- "What's the most surprising is that there was ever an agreement to meet in the first place. I always assumed this was going to be a long, difficult negotiation and this was just the first demonstration of that." Texas Sen. John Cornyn, Majority Whip

-- "It's another embarrassment for the country ... It's no way to run a government ... This is not ding dong school. It's serious." Rep. Eliot Engel, D-NY

-- "Kim Jong Un is a murderous despot and habitual liar. The President made the right call to cancel this summit. If North Korea wants diplomacy, it should know that half-measures and spin about its nuclear program won't cut it." Sen. Ben Sasse, R-Neb.

--"(Kim Jong Un is) the big winner. And when he got this letter from the president saying, 'OK, never mind,' he must be having a giggle fit, right there now in North Korea ... clearly (President Trump) didn't know what he was getting into and now he's walking away from it in this very chummy palsy-walsy letter." House Democratic leader Nancy Pelosi

-- "It's not a massive surprise the summit has been cancelled ... It's very Trumpian to break up with Kim before Kim breaks up with him." James Acton, co-director of the Nuclear Policy Program at Carnegie Endowment for International Peace

-- "Over the past many days we had endeavoured to do what Chairman Kim and I had agreed to do which was to put preparation teams together to begin to work to prepare for the summit and we had received no response to our inquiries from them. I think the American team is fully prepared. I think we're rocking. I think we're ready. I think we're prepared for this meeting." Secretary of State Mike Pompeo

-- "The rejection by Trump of conducting the American-North Korean summit undoubtedly is a serious blow to peaceful settlement in the region." Konstantin Kosachev, chairman of the foreign affairs committee in the upper house of the Russian parliament

-- "While it is regrettable that we are back to comparing the size of our nuclear arsenals, the decision to call off the summit was the necessary result of a poor negotiating strategy in which the President made it all too clear to North Korea that he needed the summit more than the North Korean dictator." Rep Adam Schiff, D-CA

-- "The North Korean regime has long given ample reason to question its commitment to stability. We must continue to work with our allies toward a peaceful resolution, but that will require a much greater degree of seriousness from the Kim regime. At the same time, Congress has provided significant tools to hold North Korea accountable, and it is important that the United States not relent in this maximum pressure campaign." House Speaker Paul Ryan, R-WI