SEOUL, South Korea — North Korea has rescinded its invitation for a senior American diplomat to travel to Pyongyang on a mission to secure the release of an American Christian missionary imprisoned on charges of committing hostile acts against the government, the State Department said on Friday.

The diplomat, Robert King, Washington’s ambassador for North Korean human rights issues, had been scheduled to fly from Tokyo to Pyongyang on Friday. The State Department had earlier said that Mr. King intended to request a pardon and amnesty for the missionary, Kenneth Bae, a Korean-American from Washington State.

“We are surprised and disappointed by North Korea’s decision” to revoke the invitation, a State Department spokeswoman, Marie Harf, said in a statement. “We have sought clarification from the D.P.R.K. about its decision and have made every effort so that Ambassador King’s trip could continue as planned or take place at a later date.” D.P.R.K. stands for the North’s official name, the Democratic People’s Republic of Korea.

It remained unclear why North Korea had retracted its invitation. The State Department statement said Mr. King planned to return to Washington on Saturday.