The United States is calling for North Korea to release American citizen Kenneth Bae who was sentenced to 15 years of hard labor by the communist state this week.

State Department Acting Deputy Spokesperson Patrick Ventrell told reporters Thursday that the U.S. is concerned about the lack of transparency and due process in North Korea and Bae should be granted amnesty and immediate release.

Ventrell said Washington understands that a North Korean court convicted Bae, a Korean American, for hostile acts against the North and sentenced him to 15 years of compulsory labor.

Asked if the U.S. government thinks Bae is innocent, Ventrell said he doesn’t know the facts of the case. He explained that Sweden is the U.S.’ protecting power and has had a few chances to meet with Bae, but there hasn't been transparency in the case.

Concerning the possibility of a special envoy traveling to North Korea to seek Bae’s release, Ventrell said a couple of former presidents had their spokespeople clarify they weren't going to Pyongyang.