WASHINGTON: Former New Mexico governor Bill Richardson and Google chairman Eric Schmidt will head to North Korea next week on a "private humanitarian mission," Richardson's office said.

Richardson, a veteran troubleshooter on North Korea, will hold a press conference at the airport in Beijing on Thursday, his office said in a statement Saturday, adding that no journalists would be accompanying the delegation.

The US State Department has voiced concerns about the trip, saying it was ill-timed in the wake of Pyongyang's widely condemned rocket launch last month.

"We are not accompanying them. We are not sending any messages with them," spokeswoman Victoria Nuland told reporters Friday. "I'm not going to get into the details of our discussions with them, except to say that they are well aware of our views that the timing of this is not great from our perspective."

Richardson has said the trip is linked to North Korea's arrest late last year and planned prosecution of a US citizen of Korean descent.

The former US ambassador to the United Nations has been to North Korea a number of times in the past 20 years and has been involved in negotiating the release of US citizens detained in the isolated state.

Accompanying the pair will be Richardson's longtime aide on North Korea, K.A. "Tony" Namkung, Jared Cohen, director of Google Ideas, a think tank run by the California-based Internet giant, and some staff, the statement said.

Spokespeople for both Richardson and Schmidt did not immediately respond to requests from AFP for further details about the trip.

Richardson said Friday he hoped the trip would be "positive", and dismissed US concerns about the mission, saying it had already been postponed once at Washington's request and that the State Department should not be "nervous."

He stressed he and Schmidt would be traveling as private citizens, representing neither the US government nor Google.

"We will make an assessment and see what comes of our visit. I think it will be positive," Richardson told CNN.

"We're not representing the State Department, so they shouldn't be that nervous," he said in an earlier interview with CBS.

The son of Kenneth Bae, the detained American, contacted Richardson and asked for his assistance, the former governor said.

The US citizen, who was arrested in November, entered the country as a tourist according to North Korea's official Korean Central News Agency (KCNA), which said he had admitted committing a crime against the state.

Pyongyang has in the past agreed to hand over detainees to high-profile delegations led by the likes of former US president Bill Clinton, and some observers suggested it may have requested Schmidt's participation in this case.

The former New Mexico governor said while a meeting with North Korean leader Kim Jong-Un was "very doubtful," he expected to meet with several senior officials.

Richardson was last in Pyongyang in 2010 when he met North Korea's chief nuclear negotiator in an attempt to ease tensions after Pyongyang shelled a South Korean border island.

He acknowledged Friday that the situation on the Korean peninsula remained tense and that he was getting "mixed messages" about Pyongyang's intentions after the North angered the West in December by launching a rocket.

"These launches the North Koreans have undertaken are not conducive to negotiations and the international community's feeling of comfort with discussing issues with North Korea," Richardson told CNN.

Pyongyang defended the launch as a purely scientific mission aimed at placing a satellite in space, but the international community saw it as a disguised ballistic missile test that flagrantly violated UN resolutions.

When asked about the trip, Nuland also said: "Frankly we don't think the timing of this is particularly helpful... in light of recent actions by (Pyongyang)," referring to the rocket launch.