SEOUL, South Korea — North Korea said on Friday that it had charged an American citizen detained there with committing “hostile acts against the republic,” a crime punishable by years in prison, at a time when the United States is pushing for new sanctions against the reclusive country for a recent rocket launching.

The North’s state-run Korean Central News Agency said that the American, identified as Bae Jun-ho, had entered the country on Nov. 3 through a port city near the Russian border. Human rights activists in South Korea said they believed Mr. Bae to be Kenneth Bae, 44, who they reported earlier this month was being held in the North.

In recent years, North Korea has detained several Americans, in some cases agreeing to free them only after high-profile Americans visited the North Korean capital, Pyongyang, to seek their release. Analysts have suspected North Korea’s leaders of trying to use such detentions to counter Washington’s diplomatic pressure over its nuclear and missile programs and force the United States to engage with them.

The North Korean report said, without elaborating, that an investigation had established Mr. Bae’s guilt and that he had confessed. It said he had been allowed to meet with officials from the Swedish Embassy in Pyongyang. The Swedish Embassy intervenes on Washington’s behalf on issues involving Americans in North Korea; the United States has no diplomatic relations with the North.