Terri Chung, left, and her mother, Myunghee Bae, right, look at a letter sent from their brother and son, Kenneth Bae, as they sit in Bae's home Wednesday, Aug. 7, 2013, in Lynnwood, Wash. (Ted S. Warren/AP)

An American Christian missionary imprisoned in North Korea last year could be freed within days on humanitarian grounds, the Obama administration said Tuesday.

Kenneth Bae’s family says he is in deteriorating health and lost roughly 50 pounds during months in a prison work camp. He was moved to a hospital this month.

In a deal worked out with the secretive regime, Robert King, a U.S. special envoy, will travel to North Korea on Friday and request a pardon for Bae before returning with the American, U.S. officials said.

Bae, 45, was detained in November 2012 as he led a missionary tour in North Korea, where few Americans are permitted to travel. He was sentenced in May to 15 years of hard labor after North Korea’s Supreme Court convicted him of state subversion. The Californian was accused of using a tourism business to undermine the government.

The United States called for Bae’s release on humanitarian grounds. Bae suffers from chronic diabetes and other medical complications, his family has said.

This 2011 file family photo provided by Terri Chung shows Kenneth Bae. Bae, the latest of several Americans jailed by North Korea in recent years, has already waited longer for his freedom than any of the others had to. (Terri Chung/Via AP)

Shortly after the conviction, Washington began a quiet outreach to North Korea through Pyongyang’s office at the United Nations, a senior Obama administration official said. After roughly four weeks without a response from North Korea, intensive talks began about two weeks ago, said the official, who requested anonymity to describe the unusual communication.

Bae’s imprisonment spanned a period of escalating tension between North Korea and the United States, as well as other nations that tried unsuccessfully to persuade new leader Kim Jong Un not to conduct a third nuclear test or test-fire a long-range missile.

Tensions cooled somewhat this spring, after China leaned hard on its impoverished ally to reduce provocations directed at the United States and South Korea.

Bae’s release, if it comes, would follow a pattern of North Korean negotiations in which a prominent American official travels to North Korea to secure a favor and the regime portrays his presence as a sign of its power.

Two American journalists arrested in 2009 were detained until former President Bill Clinton traveled to North Korea to negotiate their release.