WASHINGTON — Former President Jimmy Carter was preparing to leave for North Korea today to try to gain the freedom of an American imprisoned for illegally entering the communist nation, U.S. officials said Monday night.

North Korea agreed to release Aijalon Mahli Gomes if Carter were to come to bring him home, a senior U.S. official said. Gomes, of Boston, who was arrested Jan. 25 after entering North Korea, was sentenced in April to 8 years in prison and fined $700,000.

Carter was expected to spend a single night in North Korea and return with Gomes on Thursday, a second U.S. official said. Both officials spoke on condition of anonymity because of the sensitivity of the situation.

As was the case when former President Bill Clinton went to North Korea last summer to win the release of two detained American reporters, no U.S. officials will travel with Carter, the senior official said.

Carter spokeswoman Deanna Congileo and several other officials with the Atlanta-based Carter Center did not immediately return calls for comment. The magazine Foreign Policy first reported the Carter trip on Monday.

The senior U.S. official stressed Carter was not representing the U.S. government.