The United States should consider resuming talks with North Korea if it keeps showing restraint in the face of South Korean drills, a US troubleshooter said Thursday after a visit to Pyongyang.

Bill Richardson said a resumption of six-nation talks -- under which North Korea earlier agreed to give up its nuclear weapons in return for aid -- could help prevent a new escalation of tensions in the region.

If "they don't react militarily again to this recent drill, then maybe the time has come for the six-party talks," said the New Mexico governor, who has longstanding contacts with North Korea.

"Maybe say to the North Koreans, okay, we're going to give you another chance, let's negotiate. Get rid of your nuclear weapons -- in exchange perhaps you get some food, fuel, an end of sanctions," Richardson told CNN.

"What we don't want is a conflagration there," he said.

Richardson, a former US ambassador to the United Nations, said he was expressing his own views but was briefing President Barack Obama's administration on his trip.

Richardson said he secured promises from North Korea not to respond to South Korea's live-fire drills. The US ally has been putting on a show of force after the North killed four people including civilians in shelling last month.

North Korea last year stormed out of the six-nation talks but has since sought a resumption. The Obama administration has refused to sit down until North Korea clearly recommits to its past promises to give up nuclear weapons.

Despite holding fire over the drills, North Korea said Thursday that it was ready for "sacred war" using nuclear weapons, in what the United States criticized as "heated rhetoric."

The six-nation talks comprise China, Japan, the two Koreas, Russia and the United States.