SEOUL/WASHINGTON (Reuters) - U.S. President Donald Trump said on Wednesday that North Korea no longer posed a nuclear threat and his top diplomat offered a hopeful timeline for “major disarmament,” despite skepticism at home that Pyongyang will abandon its nuclear weapons following this week’s summit.

Trump and North Korean leader Kim Jong Un issued a joint statement after their historic meeting in Singapore on Tuesday that reaffirmed the North’s commitment to “work toward complete denuclearization of the Korean Peninsula” and gave U.S. guarantees of security to North Korea.

Democratic critics in the United States said the agreement was short on detail and the Republican president had made too many concessions to Kim, whose country is under U.N. sanctions for its nuclear and weapons programs and is widely condemned for human rights abuses.

Just over half of Americans approve of how Trump has handled North Korea, but only a quarter think the summit will lead to the denuclearization of the Korean Peninsula, according to a Reuters/Ipsos opinion poll released on Wednesday.

North Korea’s state media hailed the summit as a success, including highlighting Trump’s surprise announcement after the meeting that the United States would stop military exercises with South Korea, which the North has long sought.

Despite the lack of detail in the summit agreement, Trump stressed at a news conference afterward that he trusted Kim to follow through. He returned to Washington early on Wednesday and hailed the meeting, the first between a sitting U.S. president and a North Korean leader, as a major win for American security.

“Everybody can now feel much safer than the day I took office,” Trump tweeted. “There is no longer a nuclear threat from North Korea. Meeting with Kim Jong Un was an interesting and very positive experience. North Korea has great potential for the future!”

Kim also returned home, the North’s official news agency said.

Secretary of State Mike Pompeo, who is charged by Trump with leading follow-on negotiations, said the United States hoped to achieve “major disarmament” by North Korea within the next 2-1/2 years.

Democratic lawmakers pointed out that North Korea had often made similar statements in the past about “denuclearization,” all the while developing nuclear weapons and ballistic missiles that could be capable of striking the United States.

‘MISSION ACCOMPLISHED?’

“One trip and it’s ‘mission accomplished,’ Mr. President? North Korea still has all its nuclear missiles, and we only got a vague promise of future denuclearization from a regime that can’t be trusted,” said Adam Schiff, the top Democrat on the U.S. House of Representatives Intelligence Committee.

“North Korea is a real and present threat. So is a dangerously naive president,” he wrote on Twitter.

Senator Chris Van Hollen, also a Democrat, said of Trump’s tweet about North Korea no longer presenting a threat: “This is truly delusional.”

Trump also downplayed concerns about Kim’s human rights record. In an interview with Fox News broadcast on Wednesday, Trump said: “A lot of other people (have) done some really bad things. I could go through a lot of nations where a lot of bad things were done.”

The summit statement provided no details on when Pyongyang would give up a nuclear weapons program or how the dismantling might be verified. Skeptics of how much the meeting achieved pointed to the North Korean leadership’s long-held view that nuclear weapons are a bulwark against what it fears are U.S. plans to overthrow it and unite the Korean Peninsula.

Speaking to reporters on a trip to Seoul, where he went to brief South Korean officials, Pompeo was asked if he would like to accomplish major nuclear disarmament within Trump’s current term, which ends in January 2021. He replied: “Oh yes, most definitively.

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“Absolutely ... you used the term major, major disarmament, something like that? We’re hopeful that we can achieve that in the 2-1/2 years.”

The United States has long insisted on complete, verifiable and irreversible denuclearization by North Korea, but in the summit statement, North Korea committed only to the “complete denuclearization of the Korean Peninsula,” phrasing it has used in the past.

North Korea has often rejected unilateral nuclear disarmament, instead referring to the denuclearization of the peninsula. That has always been interpreted in part as a call for the United States to remove its “nuclear umbrella” protecting South Korea and Japan.

Pompeo bristled at a question about why the words “verifiable” and “irreversible” were not in the summit joint statement, in the context of denuclearization.

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“It’s in the statement. You’re just wrong about that. ... Because complete encompasses verifiable and irreversible. I suppose you could argue semantics, but let me assure you that it’s in the document,” Pompeo said.

Pressed on how the agreement would be verified, he said:

“Of course it will. ... I find that question insulting and ridiculous and frankly ludicrous.”

‘SAVE A FORTUNE’

Despite Trump’s assertion about the North Korean nuclear threat being over, a senior U.S. official responsible for studying the North Korean military said the U.S. intelligence assessment of the nuclear and other military threat posed by North Korea to U.S. and allied forces and bases in Asia and the northwest Pacific remained unchanged.

But the Office of the Director of National Intelligence, which assesses threats to U.S. national security, declined to comment on the president’s assertion. It also declined to reaffirm a February 2018 assessment in which it said: “North Korea will be among the most volatile and confrontational WMD (weapons of mass destruction) threats to the United States over the next year.”

In a post-summit announcement that appeared unexpected even to South Korean President Moon Jae-in, Trump said on Tuesday the United States would stop military exercises with South Korea while North Korea negotiated on denuclearization.

“We save a fortune by not doing war games, as long as we are negotiating in good faith - which both sides are!” he later wrote on Twitter.

U.S. Republican Senator Lindsey Graham called the cost reasoning “ridiculous,” telling CNN: “It’s not a burden onto the American taxpayer to have a forward deployed force in South Korea.”

“It brings stability. It’s a warning to China that you can’t just take over the whole region. So I reject that analysis that it costs too much, but I do accept the proposition, let’s stand down (on military exercises) and see if we can find a better way here.”

The United States maintains about 28,500 soldiers in South Korea, which remains in a technical state of war with the North after the 1950-53 Korean War ended in a truce rather than a peace treaty.

There was some confusion over precisely what military exercises Trump had promised to halt.

The U.S.-South Korean exercise calendar hits a high point every year with the Foal Eagle and Max Thunder drills, which both wrapped up last month. Another major exercise is due in August.