BEIJING — After approving plans on Friday for informal talks in New York between a North Korean delegation and former American officials, the Trump administration reversed course hours later, withdrawing approval for the North Koreans’ visas, two people who were to take part in the planned talks said.

The schedule called for the two sides to meet in early March, and arrangements were underway for the six-member North Korean group, led by Choe Son-hui, who runs the American affairs bureau of the North’s Foreign Ministry, to travel to New York.

The organizer of the talks, the National Committee on American Foreign Policy, led by Donald S. Zagoria, was told by the State Department on Friday morning that the visas would be granted.

But the decision was reversed in the afternoon when “someone overruled State,” said one person who planned to participate in the talks. Both of the people on the participants’ list spoke on the condition of anonymity because of the delicacy of the matter.