The U.S. government kept pressing North Korea Tuesday to free an American citizen after a trip there by his mother did not lead to his release.

State Department spokeswoman Jen Psaki said "we remain gravely concerned about" the fate of Kenneth Bae, a 45-year-old Korean-American man held in the communist nation for almost a year.

"We continue to urge the North Korean authorities to grant him special amnesty and immediate release," she said at a press briefing. "I don't have any other updates."

Bae's mother, a resident of Seattle, made a five-day trip to Pyongyang and left Tuesday (local time). During her visit she met with her son three times. She came back with him still there.

Psaki said her department has no information yet on whether has the mother has returned to the U.S. or is on her way back.

Psaki would not discuss the North's intentions for allowing Bae's mother to visit.

"I just don't have any further analysis. That's hard for me to do in terms of getting into their heads and determining what it means or what message they're trying to send," she said.

Bae, known as a Christian missionary, was arrested in North Korea in November after entering the nation with a group of tourists from China. The North later announced that its highest court had sentenced him to 15 years of compulsory labor for committing an unspecified crime against the state.

In late August, Amb. Robert King, special envoy for North Korean human rights issues at the State Department, had planned to visit Pyongyang to negotiate his release.

But North Korea abruptly canceled an invitation for King. (Yonhap News)