By Anna Fifield | Washington Post

SEOUL – A team of U.S. officials crossed into North Korea on Sunday for talks to prepare for a summit between President Donald Trump and Kim Jong Un, as both sides press ahead with arrangements despite the question marks hanging over the meeting.

Sung Kim, a former U.S. ambassador to South Korea and former nuclear negotiator with the North, has been called in from his posting as envoy to the Philippines to lead the preparations, according to a person familiar with the arrangements.

He crossed the line that separates the two Koreas to meet with Choe Son Hui, the North Korean vice foreign minister, who said last week that Pyongyang was “reconsidering” the talks. Kim and Choe know each other well – both were part of the delegations that negotiated the 2005 denuclearization agreement through the six-party framework.

Start your day with the news you need from the Bay Area and beyond.

Sign up for our new Morning Report weekday newsletter.

Kim is also joined by Allison Hooker, the Korea specialist on the National Security Council, and an official from the Defense Department. Randall Schriver, the assistant secretary of defense for East Asia and one of the officials who accompanied Secretary of State Mike Pompeo to Pyongyang earlier this month, also is in Seoul at the moment. However, it could not be immediately confirmed whether he was the Pentagon official involved in Sunday’s talks.

The meetings are expected to continue Monday and Tuesday at Tongilgak, or “Unification House,” the building in the northern part of the DMZ where Kim Jong Un met South Korean President Moon Jae-in Saturday for impromptu talks aimed at salvaging the summit, scheduled to be held in Singapore.

The two delegations are focused on the substance of any summit between the Trump and Kim Jong Un: the issue of North Korea’s nuclear weapons program.

After Saturday’s surprise inter-Korean talks, South Korean President Moon Jae-in said Kim was still committed to the “complete denuclearization” of the Korean Peninsula. But Moon declined to define “complete denuclearization,” suggesting that there are still fundamental gaps on the key issue bedeviling preparations.

The South Korean president, who is playing something of a mediator role in the talks, was optimistic after his meeting at the weekend, his second in a month with Kim Jong Un. “We two leaders agreed the June 12 North Korea-U. S. summit must be successfully held,” he said.

Given all the ups and downs with the summit, many analysts were relieved to hear that Sung Kim had been enlisted to help, especially given the retirement of fellow seasoned diplomat Joseph Yun in February.

“This is a great step,” said Vipin Narang, a nuclear nonproliferation expert at MIT, noting that the summit preparation was best handled by experts behind the scenes rather than in public forums like Twitter.

“This is how progress is made, and the best chance to have a summit, and one that yields meaningful outcomes,” Narang said.

Sung Kim, who was born in South Korea, was a key diplomat in the 2005 six-party talks. He served as ambassador to South Korea from 2011 to 2014, then became special representative for North Korea Policy, a position that Yun later took over and that is now vacant.

His North Korean counterpart, Choe, also has years of experience working on these issues and is well connected within the North Korean hierarchy.

She has also served as a nuclear negotiator and led the U.S. affairs division in the North Korean Foreign Ministry until being promoted to vice foreign minister this year. The daughter of a former premier, she is also thought to have direct access to Kim Jong Un.

Most analysts still thinks it is extremely unlikely that North Korea will surrender its nuclear weapons. The United States has been pushing for “complete, verifiable and irreversible dismantlement” – a high bar that would require North Korea to relinquish its entire nuclear program and allow international inspectors to verify this.

North Korea, which refers to its nuclear weapons program as its “treasured sword” keeping the country safe, has repeatedly said that it is not interested in unilateral disarmament.

Still, it might be able to narrow the gap. “This is an opportunity to find out what, in fact, they might be willing to do and vice versa – and that is the most important step right now,” Narang said.

The April 27 inter-Korean summit, which produced a vague declaration to work toward denuclearization and a peace treaty for the Korean Peninsula, was meant to serve as a springboard for talks between the U.S. and North Korean leaders.

Trump surprised the South Koreans in March by hastily agreeing to meet Kim in a summit, the first such meeting between a sitting American president and a North Korean leader.

But the preparations had become increasingly tumultuous as the summit date draws nearer.

After North Korean officials, including Choe, lashed out at Vice President Mike Pence and national security adviser John Bolton, Trump abruptly announced that he was canceling the talks, citing North Korea’s “tremendous anger.”

But after a magnanimous statement from North Korea on Friday, which said Kim still hoped to meet Trump “at any time,” the summit appears on again.

“We are having very productive talks with North Korea about reinstating the Summit which, if it does happen, will likely remain in Singapore on the same date, June 12th., and, if necessary, will be extended beyond that date,” Trump tweeted Friday night.

The White House has said that preparations will continue while the final decision on whether to proceed with the summit, scheduled to be held in Singapore, is made.

Trump confirmed Saturday that working-level meetings were continuing. “As you know there are meetings going on as we speak in a certain location which I won’t name, but you’d like the location,” he told reporters in Washington.

Reading this on your iPhone or iPad? Check out our new Apple News app channel here and click the + at the top of the page to save to your Apple News favorites.

A separate U.S. team led by Joe Hagin, deputy chief of staff in the White House, is organizing logistics with Kim Chang Son, who is effectively the North Korean leader’s chief of staff.