Robert King, the U.S. special envoy for North Korean human rights, has canceled his trip to South Korea, diplomatic sources said Sunday.

Multiple sources said King, who had been scheduled to arrive in Seoul on Sunday, has abruptly called off his trip without giving a reason.

King had been set to spend five days in South Korea and meet with officials from the foreign ministry and other government agencies for talks on North Korean human rights issues. King had also been slated to give speeches at conferences on North Korean human rights and North Korean policies.

Sources suspect King’s sudden change of plans may be connected with the detention of a Korean-American man in North Korea.

Kenneth Bae, 44, has been sentenced to 15 years of hard labor for an unspecified crime. North Korea has accused him of attempting to overthrow the North Korean regime.

King had been expected to discuss Bae’s situation with South Korean officials here and sources believe King may be trying to contact North Korean officials to discuss Bae’s release.

In 2011, with a Korean-American Jun Young-soo detained in North Korea, King flew to Pyongyang to help gain Jun’s release.

Former U.S. Presidents Bill Clinton and Jimmy Carter have previously traveled to Pyongyang to bring home detained American citizens. The U.S. has no formal diplomatic ties with North Korea.

Earlier this month, the North said it has no plan to invite anyone from the U.S. over Bae’s detention, saying he is not a “political bargaining chip” in talks with Washington as many believe. (Yonhap News)