President Donald Trump says Democrats' decision to question his former lawyer, Michael Cohen, while he was overseas may be a reason his talks with North Korean leader Kim Jong Un failed. "For the Democrats to interview in open hearings a convicted liar and fraudster at the same time the very important nuclear summit with North Korea is perhaps a new low in America politics and may have contributed to the ‘walk,’" Trump tweeted late Sunday. He was referring to his decision to leave Hanoi without making any deals with Kim over North Korea's nuclear ambitions. Cohen, who was Trump's lawyer for a decade, called the president a liar, crook and racist during his testimony to Congress. He strongly implied Trump committed crimes while president, leading Democrats to call for more investigations. Although Trump did not say exactly how the Cohen hearings affected the summit, he said, "Such things are never done when a president is overseas. Shame."But U.S. National Security Advisor John Bolton appeared on several Sunday morning talk shows to say last week's summit between Trump and Kim was not a failure, even though talks fell apart with no agreements."He's not desperate for a deal -- not with North Korea, not with anybody if it's contrary to American national interests," Bolton told Fox News Sunday. He also told CBS's Face the Nation, "The president held firm to his view. He deepened his relationship with Kim Jong Un. I don't view it as a failure at all when American national interests are protected."Bolton said Kim was willing to make "a very limited concession" to dismantle its Yongbyon nuclear weapons complex in exchange for "substantial" sanctions relief.Bolton described Yongbyon as "an aging nuclear reactor" and said Kim was unwilling to make a "big deal" with Trump. "It was the sanctions that brought the North Koreans to the table. It's the sanctions they want relief from and relief they can get if they denuclearize," Bolton saidBolton conceded that North Korea is continuing to produce nuclear fuel and said while "there is no expiration date" on further talks, future negotiations with North Korea are in limbo.Bolton also appeared on CNN's State of the Union, where he defended Trump who said he took Kim "at his word" when the North Korean leader claimed he knew nothing about the alleged torture of imprisoned U.S. student Otto Warmbier.The Ohio student fell into a coma in a North Korean prison and died shortly after he was sent home two years ago.Bolton said while Trump accepts what Kim said, it does not mean he accepts it as reality."The president's been very clear he viewed what happened to Otto Warmbier as barbaric and unacceptable and I think the best thing North Korea could do right now would be to come up with a full explanation of exactly what happened to him," Bolton said on CNN.The Democratic head of the House Intelligence Committee Adam Schiff called the entire summit a "spectacular failure" and said Trump made things worse with his comments about Otto Warmbier."This the result of a president who is not prepared for these kind of negotiations, a staff that is not well-prepared and that is essentially flying by the seat of its pants," Schiff said on Face the Nation.Also Sunday, Trump says the reason he canceled large-scale springtime military drills with South Korea is to save "hundreds of millions of dollars" for which the U.S. is never reimbursed."That was my position long before I became president," Trump tweeted Sunday while adding "reducing tensions with North Korea at this time is a good thing."Pentagon officials say instead of the massive war games, the U.S. and South Korea will hold a series of small-scale exercises.Washington and Seoul have traditionally held the exercises every spring to test military readiness in case tensions with North Korea should boil over.The war games have always angered the North, which denounces the U.S.-South Korea joint exercises as aggressive provocation and rehearsals for war.