President Obama returns to Washington today after a busy week in Asia. His final stop was South Korea where he announced plans to send an envoy to North Korea for direct talks on its nuclear weapons program.

New Mexico Governor Bill Richardson has experience negotiating with North Korea and has made numerous trips to the communist country. He spoke to John Roberts on CNN's "American Morning" Thursday.

Read more: Obama to send envoy to North Korea

[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2009/US/08/05/nkorea.journalists/art.family.afp.gi.jpg caption="Freed journalists Euna Lee and Laura Ling after being released from North Korea on August 5, 2009."]

We arrived at the frozen river separating China and North Korea at 5 o'clock on the morning of March 17. The air was crisp and still, and there was no one else in sight. As the sun appeared over the horizon, our guide stepped onto the ice. We followed him.

We had traveled to the area to document a grim story of human trafficking for Current TV. During the previous week, we had met and interviewed several North Korean defectors - women who had fled poverty and repression in their homeland, only to find themselves living in a bleak limbo in China. Some had, out of desperation, found work in the online sex industry; others had been forced into arranged marriages.

Now our guide, a Korean Chinese man who often worked for foreign journalists, had brought us to the Tumen River to document a well-used trafficking route and chronicle how the smuggling operations worked.

There were no signs marking the international border, no fences, no barbed wire. But we knew our guide was taking us closer to the North Korean side of the river. As he walked, he began making deep, low hooting sounds, which we assumed was his way of making contact with North Korean border guards he knew. The previous night, he had called his associates in North Korea on a black cellphone he kept for that purpose, trying to arrange an interview for us. He was unsuccessful, but he could, he assured us, show us the no-man's land along the river, where smugglers pay off guards to move human traffic from one country to another.

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(CNN) - Journalists Laura Ling and Euna Lee told Ling's sister they were treated humanely in North Korea, and they believe they weren't sent to hard-labor camps because they have medical conditions, Lisa Ling said Friday.

The sister, speaking on CNN's "American Morning," did not elaborate on the medical conditions, but said her sister will soon tell her story.

"Laura is eager to tell the story about what happened. I want to let her do so, but right now, she's really getting reacclimated. The processes are slow. She's very, very weak," Lisa Ling said, adding that the stories she's heard so far are "jaw-dropping."

Laura Ling and Lee were working for California-based Current TV, a media venture of former Vice President Al Gore, when they were arrested in March for crossing the border between China and North Korea.

Lisa Ling said that before they left the United States, the pair never intended to cross into North Korea. They have acknowledged that they briefly did, however, and they were convicted of entering the country illegally to conduct a "smear campaign" against the reclusive Communist state.

They were sentenced in June to 12 years of hard labor. North Korea's leader, Kim Jong Il, pardoned the women Tuesday after meeting with former President Bill Clinton. They arrived home the following day.