Story highlights Dennis Rodman: "Do me a solid and cut Kenneth Bae loose"

Bae was sentenced to 15 years of hard labor in North Korea for unspecified "hostile acts"

His sister says Bae owns a tour company and is not a spy

Rodman has called North Korean ruler Kim Jong Un a "friend for life"

If any American has the power of persuasion over North Korea's defiant young ruler, it might be eccentric ex-basketball star Dennis Rodman.

So when Rodman digitally called for Kim Jong Un to release U.S. citizen Kenneth Bae , he may have a shot at a response.

"I'm calling on the Supreme Leader of North Korea or as I call him "Kim", to do me a solid and cut Kenneth Bae loose," Rodman tweeted

Bae was sentenced to 15 years of hard labor last month after he was convicted of unspecified "hostile acts" against North Korea. The country's state-run Korean Central News Agency said the Korean-American was arrested November 3 after arriving as a tourist in Rason City, a northeastern port near the Chinese border.

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"He has never had any evil intentions against North Korea, or any other country for that matter," Chung said.

She said her brother owns a tour company and was in North Korea for work.

"He didn't have any problems going there last time, last year five times, so he didn't have any reason to suspect that there would be any trouble this time around," she said.

U.S. officials have struggled to establish how exactly Bae fell afoul of North Korean authorities. The North Korean statement on his conviction provided no details of the allegations against him.

"This was somebody who was a tour operator, who has been there in the past and has a visa to go to the North," a senior U.S. official told CNN on Monday, speaking on condition of anonymity because of the diplomatic sensitivity of the issue.

But NK News, a U.S.-based website that focuses on North Korea, suggests Bae has served as a missionary trying to convert North Koreans.

"I knew that Jesus wanted me to be a 'channel' to the North," Bae told a Korean congregation at a St. Louis church in 2011, NK News reported . "This year, I'm working at taking several short term missionary teams into North Korea."

Bae's sentencing came after weeks of intense rhetoric from North Korea, which conducted its third nuclear test in February and launched a satellite into orbit atop a long-range rocket in December.

Washington responded by deploying additional missile interceptors on the West Coast, dispatching a missile defense system to the Pacific territory of Guam and bolstering annual U.S.-South Korean military exercises with overflights by nuclear-capable B-2 and B-52 bombers.

Rodman, the heavily pierced NBA Hall of Famer, made headlines when he befriended North Korea's supreme leader during a visit in February.

"You have a friend for life," Rodman told Kim after the two men sat next to each other watching an unusual basketball exhibition in Pyongyang

But Rodman said he is not an official diplomat between the United States and North Korea.

"I'm not a politician," he tweeted. "Kim Jung Un & North Korean people are basketball fans. I love everyone. Period. End of story."