The time is not right for a planned trip to Pyongyang by Google Executive Chairman Eric Schmidt and New Mexico's former governor Bill Richardson, the United States State Department said on Thursday.

"Frankly, we don't think the timing of this is particularly helpful, but they are private citizens, and they are making their own decisions," said State Department spokeswoman Victoria Nuland at a news conference.

The trip is ill-timed in light of the recent rocket launch by the Democratic People's Republic of Korea, she added.

Schmidt and Richardson's trip, expected to happen this month, comes at a time when the United Nations Security Council is still deliberating further moves against the DPRK over its launch of a satellite last month.

Washington and its allies claim that Pyongyang's satellite launches are disguised ballistic missile tests and violate United Nations resolutions adopted following the country's nuclear tests in 2006 and 2009.

Media reports said that Schmidt and Richardson plan to visit Pyongyang in January, and that the trip is linked to the US citizens recently detained by the DPRK.

The visit has not been officially confirmed by either Google or Richardson.

DPRK media reported that a US citizen has been detained for committing a "hostile act" in November, and the US citizen — identified as Pae Jun-ho — entered the country as a tourist and has admitted that he committed 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. Some observers suggested the country may have requested Schmidt's participation in this case, AFP reported.

Richardson is familiar to DPRK leaders. He visited the country many times in the last 20 years and was involved in negotiating the release of US citizens detained there.

In 1996, he played a major role in securing the release of US citizen Evan Hunziker.

Richardson was last in Pyongyang in 2010 when he met the DPRK's chief nuclear negotiator, in a bid to ease tensions after a border-island conflict between the DPRK and the Republic of Korea.

Nuland insisted that Schmidt and Richardson are not representatives of the US government.

"As you know, they are private citizens," she said. "They are traveling in an unofficial capacity. They are not going to be accompanied by any US officials. They are not carrying any messages from us."

Jin Canrong, a global affairs professor at Renmin University of China, said the visit also shows that Google and the DPRK want to communicate.

"The DPRK hopes to stop being isolated by the international community through Google's reputation around the world, and Google is attracted by the Internet market in the country," Jin said.