The State Department said on Thursday the time was not right for Google Inc Executive Chairman Eric Schmidt and former diplomat Bill Richardson to visit North Korea, which drew international criticism for a rocket launch last month.

State Department spokesman Victoria Nuland said Schmidt and Richardson would be traveling as private citizens, not representatives of the U.S. government.

"Frankly, we don't think the timing of this is particularly helpful," Nuland told reporters, citing North Korea's launch of a long-range rocket in December. "They are well aware of our views."

Reports of Schmidt's plan emerged as the United States, South Korea, Japan and their European allies were pushing at the United Nations to expand long-standing U.N. Security Council sanctions on North Korea after the North's December 12 rocket launch.

A source familiar with the matter on Thursday confirmed an Associated Press report that Schmidt planned to visit North Korea with Richardson, a former governor of New Mexico, former U.S. ambassador to the United Nations and diplomatic troubleshooter.

The AP said Schmidt, a top figure in the U.S. technology industry and a key executive at the world's leading search engine company, could visit as early as this month, but added it was unclear which people he would meet or what his agenda is.

Google espouses a mission of organizing the world's information and making it universally accessible and useful. North Korea is one of the world's most repressive states, with Internet access limited largely to the most influential officials and media content rigidly controlled.

Nuland stressed Schmidt and Richardson were not acting on behalf of the United States.

"We are obviously aware of the trip that has been announced," she said, later correcting herself to say that the department was aware of media reports about the trip.

"They are private citizens. They are traveling in an unofficial capacity," she said. "They are not going to be accompanied by any U.S. officials. They are not carrying any messages from us. They are private citizens and they are making their own decisions."

On Wednesday, Google did not respond directly to a question about whether Schmidt was going to North Korea, although a spokeswoman's response suggested a visit would not be for company business.

"We do not comment on personal travel," spokeswoman Samantha Smith said on Wednesday when asked about the AP report.

On Thursday, a Google spokeswoman and Richardson's office did not respond to emails seeking comment about the State Department's remarks.

A possible second aspect of Schmidt's visit as part of Richardson's delegation could be to try to obtain the release of Korean-American tourist Kenneth Bae, detained and accused of unspecified crimes against the state. Richardson has helped negotiate the release of detained Americans in the past.

North Korea said its December rocket launch put a weather satellite in orbit, but critics say it was aimed at nurturing the kind of technology needed to deliver a nuclear warhead with a long-range missile.

At the United Nations, council diplomats say North Korea's chief ally China so far has resisted U.S. and allies effort to expand sanctions imposed on Pyongyang in response to nuclear and missile tests in 2006 and 2009. The issue is now a bilateral one between Washington and Beijing, the diplomats said.