A North Korean soldier fled across a heavily fortified border to defect to South Korea, just as the rivals began taking steps to reduce military tensions.
North Korea is accusing the Trump administration and some supporters of trying to "stoke confrontation" instead of promoting peace efforts.
North Korea: Kim Jong Un observed the successful test of an unspecified "newly developed ultramodern tactical weapon," according to reports.
Pompeo was supposed to meet with Kim Yong Chol in New York on Thursday to discuss North Korea's commitment to eliminating its nuclear weapons.
The U.S. military has ordered extra scrutiny for South Koreans who want to visit friends or attend events on American bases in Japan.
South Korea is proposing that the United States hold off on a demand for an inventory of North Korea's nuclear weapons and accept the verified closure of a key North Korean nuclear facility as a next step in the negotiations, Seoul's top diplomat said in an interview with The Washington Post.
A peace treaty involving the U.S., China and North Korea should only be contemplated once it has been determined that North Korea is denuclearized.
South Korea government officials estimate that the size of North Korea's nuclear arsenal ranges from at least 20 bombs to as many as 60.