Updated

A U.S. envoy will travel to North Korea later this week to try and secure the release of an American missionary sentenced to 15 years hard labor in the country earlier this year.

The State Department says in a statement Bob King, who is special envoy for North Korean Human Rights Issues, will travel to North Korea on a humanitarian mission Aug. 30 to request freedom and a pardon for 45-year-old Kenneth Bae.

"Ambassador King will request the DPRK pardon Mr. Bae and grant him special amnesty on humanitarian grounds so that he can be reunited with his family and seek medical treatment," the statement said.

Bae, a tour operator and Christian missionary, was arrested in November and accused of subversion. In April, North Korea's Supreme Court convicted him of committing hostile acts against the country and sentenced him to 15 years hard labor.

Bae was recently hospitalized and reportedly has lost 50 pounds since he was sentenced.

While King's visit is a humanitarian mission, it could help improve relations severely strained by Pyongyang's pursuit of nuclear weapons.

"We remain deeply concerned about the health and welfare of Kenneth Bae, the American citizen currently detained in North Korea," the White House said in a statement. "We urge the government of North Korea to grant special clemency to Mr. Bae immediately and allow him to return home with Ambassador King."

When King last visited North Korea in May 2011 to assess the impoverished North's food situation, he came home with Eddie Jun, the last American to be held then freed by Pyongyang. Jun, a Korean-American from California, was arrested for alleged unauthorized missionary work during several business trips to the country. He was released on humanitarian grounds.

Bae's sister revealed earlier this month that he was moved from a labor camp to a hospital after losing more than 50 pounds. Terri Chung, of Edmonds, near Seattle, says her brother, a father-of-three, suffers from diabetes, an enlarged heart, liver problems and back pain. He was born in South Korea and immigrated to the U.S. with his parents and sister in 1985. For the past seven years Bae has been living in China, Chung says.

According to U.S. officials, Washington first made its offer to send King to North Korea several weeks ago, but Pyongyang only recently took them up on the offer. Pyongyang has yet to declare it will release Bae.

King is already in the region, having traveled to China and then South Korea in the past week for talks with officials and activists about human rights and humanitarian issues in North Korea. He is scheduled to be in Japan on Wednesday.

Rep. Rick Larsen, who represents the Washington state district where Bae is from, said he was encouraged by the State Department's decision to send King and commended their efforts to seek Bae's release.

"Kenneth's family has waited in anguish and uncertainty, but has never wavered in their tireless advocacy on his behalf," Larsen said in a statement. "I will continue working with the State Department and Kenneth's family to ensure his safe return home."

North Korea and the U.S. do not have formal diplomatic relations, and their tenuous ties have been in a tailspin for more than a year after Pyongyang conducted long-range rocket launches and a February nuclear test in defiance of U.N. Security Council resolutions. When sanctions were then tightened, North Korea issued dire threats against the U.S. and its allies.

North Korea has dialed down its rhetoric in recent months and has moved to improve its relations with rival South Korea, a staunch U.S. ally. The two sides have agreed to reopen a shuttered, joint industrial park and hold reunions of Korean families divided since the 1950-53 Korean War.

North Korea, analysts say, has previously used detained Americans as bargaining chips in its standoff with the U.S. over its nuclear and missile programs. Multination aid-for-disarmament talks have been on hold since 2009, and efforts by Washington to negotiate a freeze in the North's nuclear program in exchange for food aid collapsed 18 months ago.

Two senior Obama administration officials reportedly made secret visits to North Korea in 2012 in an effort to improve relations with the government of young leader Kim Jong Un, but apparently made little headway.

Bae is at least the sixth American detained in North Korea since 2009. The others were eventually allowed to leave without serving out their terms, some after prominent Americans, including former Presidents Bill Clinton and Jimmy Carter, visited North Korea.

In an interview posted online by a pro-North Korean newspaper this month, Bae requested that a high-ranking U.S. official should come to North Korea and seek a pardon for his release. It wasn't clear from the video whether Bae was speaking voluntarily.

The Associated Press contributed to this report