Defense Secretary Jim Mattis says the U.S. is engaged in “methodical” preparations for upcoming talks between President Trump and North Korean leader Kim Jong Un, and that everything is “on track” for the meeting, which is expected to occur in late May.

“It’s a very methodical process getting together with our allies, Japan and ROK, the Republic of Korea,” Mattis said in an impromptu gathering with Pentagon reporters Tuesday morning.

Mattis described what he called “normal consultation” with other nations that are also involved as the U.S. develops the “talking points” and the “discussion points” that the U.S. is interested in negotiating with Kim.

Mattis stressed that the process of preparing for the talks between the two leaders is a “diplomatic effort” being led by the State Department despite the lack of a confirmed secretary of state. President Trump intends to nominate CIA Director Mike Pompeo for the job.

“There’s an acting secretary right now, and the people that actually do the crafting,” Mattis said. "These are the people that roll up the sleeves and do the work.”

Mattis said what he called “changes in the national security structure” have had no effect on operations at the Pentagon and have not resulted in any significant change in policy.

“We have very strong institutions in this country, and they continue,” Mattis said.

Mattis also said he could not confirm reports that Kim may have visited Beijing in a brief trip on an armored train.

“It kinda looked like he did, but I don’t know,” Mattis said.