Former New Mexico governor Bill Richardson and Google chairman Eric Schmidt arrived Monday in North Korea, where a US citizen is being held awaiting trial, for what the politician called a private trip. "This is a private humanitarian mission, not connected to the US government," said Richardson, also a former US ambassador to the United Nations, at Beijing's airport before travelling to the secretive nation, AFP reported. "We're going to be in Pyongyang, probably for two and a half days. We may go outside the city. We will find out when we arrive," he said.