By Jack Kim and David Chance

SEOUL (Reuters) - The United States has offered to send a special envoy to North Korea to win the release of a jailed missionary, but signaled that any meaningful talks with Pyongyang will require it to give up its pursuit of nuclear weapons.

Kenneth Bae, 45, has been held for more than a year by the North, which has convicted him of trying to overthrow the state and sentenced him to 15 years hard labor.

Bae, a Korean American, was paraded in front of a group of foreign and local reporters on Monday and asked Washington to help him get home, the North's state news agency and foreign media based in Pyongyang reported.

"We hope this decision by DPRK (Democratic People's Republic of Korea) authorities to allow Kenneth Bae to meet with reporters signals their willingness to release him," a U.S. official, speaking on condition of anonymity, told Reuters on Monday.

"We have offered to send Ambassador King to Pyongyang to secure Mr. Bae's release," the official added, referring to U.S. North Korean rights envoy Robert King.

"We have asked the North Koreans this, and await their early response," the official added.

An attempt by King to secure Bae's release last August was rejected by Pyongyang.

It was not immediately clear why the North Korean authorities had allowed the event at Pyongyang Friendship Hospital, Bae's second media appearance since his arrest in 2012 when he led a tour group into the country.

North Korea's state KCNA news agency reported Bae himself had asked to hold the press conference.

Bae's sister in the United States said in a statement that while her brother appeared in decent health during the news conference, he was "distressed" and likely "worn down physically and emotionally" after 15 months of imprisonment.

Terri Chung, who lives in the Seattle area, also apologized to North Korea, pleading for her brother's release and for U.S. officials to step up clemency efforts on his behalf.

"We understand that Kenneth has been convicted of crimes under DPRK laws. Our family sincerely apologizes on Kenneth's behalf," Chung said, adding: "We humbly ask for your mercy to release my brother."

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Bae's son Jonathan urged Washington to respond to the plea.

His father's words "obviously mean that Washington has not done enough", Bae told Reuters by phone. "We need to send someone over and bring him home. That's what it's going to take. He needs to come home," he said.

U.S. READY FOR "CREDIBLE" NUCLEAR TALKS

Bae's appeal came days after reclusive North Korea demanded that South Korea and the United States halt annual military drills due in February and March and offered the South a halt to hostilities.

The North's official Rodong Sinmun continued the conciliatory note in a commentary carried on Tuesday saying the state was open to friendly ties with any country "on a basis of mutual respect and equality, even with capitalist countries."

U.S. Deputy Secretary of State William Burns said on Tuesday in Seoul that the United States and South Korea were concerned about the prospect of "further reckless behavior" from Pyongyang.

In 2013, North Korea launched a months-long barrage of threats against South Korea, Japan and the United States, saying it would stage missile and nuclear strikes, triggering a sharp escalations in tensions and military deployments.

Burns said that both Washington and Seoul were willing to return to "credible" talks but only if Pyongyang was committed to "authentic negotiations aimed at denuclearization".

He did not comment on Bae.

North Korea has undertaken three nuclear weapons tests and used its civil nuclear program as a cover to develop weapons. Pyongyang says that it will never give up its nuclear ambitions which it says are a deterrent against aggression.

Pictures of the Bae's press conference released by the North's KCNA news agency showed Bae in a drab grey prison uniform and baseball cap, although he appeared to be in reasonable health.

North Korea's Supreme Court had said Bae used his tourism business as a cover to recruit people to overthrow the government.

KCNA reported that Bae acknowledged he had broken North Korean laws and said he wanted to clarify "misinformation" surrounding his incarceration that had "enraged" the North.

"I, availing myself of this opportunity, call on the U.S. government, media and my family to stop linking any smear campaign against the DPRK and false materials with me, making my situation worse," Bae was quoted by KCNA as saying.

"I hope that I will be pardoned by the DPRK and go back to my family. I request the U.S. government, media and my family to pay deep concern and make all efforts to this end," he added, according to KCNA.

(Additional reporting by Jug-min Park in Seoul, Lesley Wroughton in Washington, and Eric M. Johnson in Seattle; Editing by Raju Gopalakrishnan)