WASHINGTON — With talks aimed at dismantling North Korea’s nuclear arsenal at an impasse, U.S. Secretary of State Michael R. Pompeo is heading to Pyongyang to meet with Kim Jong Un in hopes of reviving the process — and to set up a potential second summit with President Trump.

Pompeo said he was confident his fourth visit to North Korea this year would “advance the commitment” Kim and Trump made when they met in Singapore on June 12. But at least in public, he did not set high objectives for his trip.

“The mission is to make sure that we understand what each side is truly trying to achieve,” Pompeo said Friday, according to a reporter aboard his flight to Tokyo, his first stop on a trip that also will take him to Seoul and Beijing. He is scheduled to meet Kim early Sunday in Pyongyang.

Pompeo said he might be able to set up a tentative date and location for a second summit between Kim and Trump.

Kim had declined to meet Pompeo when he last visited the North Korean capital in July, and state media later denounced what it called Pompeo’s “gangster-like” demands. Trump abruptly cancelled another planned visit by his secretary of State in August amid concerns that Pompeo would again fail to achieve progress.

Since then, Kim has sent Trump what the president has called “beautiful letters,” and Pompeo met his North Korean counterpart, Foreign Minister Ri Yong Ho, on the sidelines of the United Nations General Assembly last week. Trump also sought to downplay criticism that his efforts had yet to produce a timetable or any other sign of denuclearization.

“If it takes two years, three years or five months — doesn’t matter,” Trump said. Several days later, he offered effusive public praise for Kim, saying at a campaign rally last weekend that he and the North Korean leader “fell in love.”

On Tuesday, apparently emboldened by those comments, state media in Pyongyang signaled that Kim’s government was toughening its negotiating position. It said the U.S. must make a declaration to formally end the 1950-53 Korean War, replacing the armistice that halted the conflict, for talks to proceed.

U.S. officials long have resisted formally ending the decades-old war amid concerns it would pressure Washington to remove its military forces from South Korea.

The White House has considered a “declaration for declaration” proposal, in which the United States would agree to formally end the war in exchange for Pyongyang producing a detailed inventory of nuclear equipment and arsenal that U.N. inspectors could then verify. But North Korea has resisted that, indicating it was not prepared to disclose those details.

“Without any trust in the U.S., there will be no confidence in our national security, and under such circumstances there is no way we will unilaterally disarm ourselves first,” Ri said at the U.N. last week.

South Korean President Moon Jae-in then suggested a compromise. In exchange for the U.S. end-of-war declaration, he offered, North Korea would agree to dismantle its vast Yongbyon nuclear facility. Kim had pledged to shut the facility, or at least parts of it, in a summit with Moon last month.

A delegation of South Korean legislators, in Washington this week to lobby Congress and State Department officials, came away with the impression that the Trump administration was still not willing to formally end the war.

Trump has repeatedly cited “tremendous progress” with North Korea, citing the release of three American prisoners in May, the return of about 50 sets of human remains from the Korean War, and the absence this year of new missile or nuclear weapons tests by Pyongyang.

After the Singapore summit, Trump surprised allies — and the Pentagon — by suspending annual joint U.S. military exercises with South Korea, and even using North Korea’s rhetoric in calling them “war games.”

But U.N. nuclear monitors and other experts say they have seen no evidence that North Korea has taken significant steps to dismantle its nuclear infrastructure or weapons facilities, and that production of fissile material that can be used as bomb fuel has not ceased.

“They cannot come out of these trips anymore with broad statements of principles,” Victor Cha, an Asia specialist in the George W. Bush White House, said Friday. “There needs to be some actual, tangible movement on the nuclear issue.”

Several U.S. experts said Kim appears increasingly determined to work only with Trump, not his deputies.

“They think they can get [the] best possible deal by directly dealing with President Trump himself,” said Sue Mi Terry, a former CIA analyst specializing in the Korean peninsula who is now a fellow at the nonpartisan Center for Strategic and International Studies.

“They truly believe this is a once-in-lifetime opportunity that they have” with Trump, Terry said. She said she believed Pompeo’s visit would focus almost exclusively on making arrangements for the next summit.

Trump’s praise for one of the world’s most ruthless and brutal dictators has jarred even some of the president’s supporters.

“I’m worried that we’re being played here,” Sen. Lindsey Graham (R-S.C.) said this week. “So I’m telling President Trump: Enough with ‘I love you.’ This is not a guy to love. ... From my point of view, this ‘love’ crap needs to stop.”

The administration also has come under pressure to ease economic sanctions, including those that target trade of fuel and minerals.

Russia and China have begun allowing some shipments into North Korea in what critics say are violations of U.N. Security Council sanctions. At the General Assembly, Russia said it would continue to do so, and Pompeo said there would be no sanctions relief until denuclearization occurs.

tracy.wilkinson @latimes.com