SEOUL, South Korea -- North Korea said Sunday that it would not use an imprisoned American citizen as a political bargaining chip, rejecting the possibility of allowing any prominent Americans to visit the North to request his release, as it has in similar cases in the past.
The United States has called for the immediate release of the prisoner, Kenneth Bae, a Korean-American who was sentenced last week to 15 years of hard labor for committing "hostile acts" against the North.
Mr. Bae, 44, was arrested in Rason, in the northeast, in November after leading a group of businessmen there from Yanji, China. The North's refusal to release him adds a new source of tension in the relationship between the United States and North Korea as Washington tries to hold a tough line with the North over its nuclear program.
Mr. Bae is the sixth American known to have been arrested in the North since 2009. The rest have been released or deported. But two were released in 2009 only after former President Bill Clinton visited Pyongyang, the North's capital, and met with Kim Jong-il, the North's leader at the time. Another was released in 2010 after a visit by former President Jimmy Carter.
This time, North Korea "has no plan to invite anyone of the U.S. as regards the issue," a spokesman for the North Korean Foreign Ministry was quoted as saying Sunday by the official Korean Central News Agency.
On Thursday, the State Department cited "longstanding concerns about the lack of transparency and due process in the North Korean legal system." But it indicated that it was not prepared, at least not for now, to let a high-profile mission visit Pyongyang to try to facilitate Mr. Bae's release.
The United States has refused to allow North Korea to use the fate of imprisoned American citizens as leverage to force the opening of official negotiations. It did not officially endorse the previous visits by Mr. Clinton and Mr. Carter. But analysts who study North Korea's behavior said North Korea, in its internal propaganda, had portrayed the visits as examples of Washington's capitulation.
On Sunday, North Korea said it had previously freed American citizens as "humanitarian" gestures because prominent Americans visited Pyongyang and "apologized for their crimes and promised to prevent the recurrence of similar incidents." But it said that Mr. Bae's case proved that "humanitarian generosity will be of no use in ending Americans' illegal acts."
"Some media of the U.S. said that the D.P.R.K. tried to use the case as a political bargaining chip," said the North Korean spokesman, using the initials of his country's official name, the Democratic People's Republic of Korea. He called those commentst "ridiculous and wrong."
Little is known about why Mr. Bae was arrested in the North. Human rights activists in South Korea have said that Mr. Bae, from Washington State, ran a tour business in China. He visited North Korea several times and was interested in helping orphans there, they said.
North Korea said Sunday that Mr. Bae entered North Korea "with a disguised identity in an intentional way under the back-stage manipulation of the forces hostile toward the D.P.R.K.," and committed "various crimes" which were "aimed at the state subversion."
During his trial, Mr. Bae confessed and admitted his crimes, the North said, according to the state media.
North Korea appears to be stepping up its efforts along its border with China to stem the flow of information and other influences from entering the country, and to stop defectors from fleeing.
The North Korean government appears to be growing more concerned about what it calls "psychological warfare" waged by its enemies to contaminate its people with corrupt Western ideas. It has repeatedly vowed that a popular revolt similar to those of the Arab Spring will not happen in the North, saying that the country is "no Libya."
In a separate statement on Sunday, North Korea demanded that South Korea stop activists from sending antigovernment leaflets into the North before it considered reopening an industrial complex jointly operated with the South. The North pulled out all its workers from there last month.
In recent years, Christian and conservative activists in South Korea have been using large balloons to send leaflets across the border. The leaflets typically contain Christian messages or criticism of the government in North Korea. South Korean police officers have blocked several attempts by activists to release their balloons in recent weeks, including one on Saturday, prompting the activists to charge that the South Korean government was capitulating to North Korean blackmail.
This article originally appeared in The New York Times.