SEOUL -- Pyongyang marked the 13th day of custody Thursday of a U.S. pilot by publishing what it said was his confession to "illegal intrusion" into North Korea, but Washington flatly denied any suggestion of espionage.


Pyongyang said Chief Warrant Officer Bobby Hall confessed on Christmas Day to flying deep into North Korean airspace and had asked for forgiveness and to be allowed home.


It released a photograph of what it said was Hall's seven-page hand written letter.


Hall's helicopter crashed in North Korea on Dec. 17. Pyongyang says it shot down the aircraft and that co-pilot David Hilemon was killed in the crash. Washington says the helicopter had strayed accidentally over North Korea.


Hall's alleged statement, which also says he was shot down, was published a day after Thomas Hubbard, U.S. deputy assistant secretary of state for East Asian and Pacific Affairs, arrived in Pyongyang to try to win his release.


Hubbard met Thursday with First Vice Minister of Foreign Affairs Kang Sok Ju, according to North Korea's official Korea Central News Agency, monitored in Tokyo.


The United States said it could not confirm Hall's confession and continued to reject North Korean charges earlier this week that the helicopter was on a spy mission.


"I admit that this criminal action is inexcusable and unpardonable. However, at home my parents, wife and kids are anxiously waiting for my return to them," Hall, 28, was quoted as saying by Pyongyang's news agency.


While never using the words "espionage" or "spying," Hall allegedly confesses to having "illegally intruded deep" into North Korea and having "deviated" from a prearranged route.


An analyst at the Unification Ministry in South Korea said the use of vocabulary was not an issue.


"Espionage is never stated, but if you read carefully, Hall talks of an 'observation reconnaissance' and this, in the North's view, means he admits spying," he said.


He said the timing of the publication was designed to gain more leverage in negotiations with the United States and added that it had all the hallmarks of a confession under duress.


U.S. State Department spokes-woman Christine Shelly said: "We continue to reject all charges of espionage, and more importantly, have not had access to Officer Hall."


President Bill Clinton appealed again Wednesday for Hall's release as pressure mounted in Congress to hold back on a breakthrough nuclear deal with Pyongyang if the case is not resolved.


Several members of Congress said that if Hall were not released, Washington should pull out of the October deal whereby North Korea agreed to suspend its nuclear program in return for supplies of fuel oil and new light-water nuclear reactors, which produce much less plutonium, an ingredient in nuclear bombs.


Officials in South Korea have expressed concern that North Korea is using Hall as a bargaining chip to squeeze concessions from Washington.


The North Koreans have returned the body of Hilemon, who was buried with full military honors Wednesday.