WASHINGTON (AFP) - A US official rejected on Monday the joking suggestion that flamboyant basketball star Dennis Rodman be made ambassador to North Korea, after his highly-watched trip to the isolated state.

"I'm not even sure I can dignify that with a response," acting State Department spokesman Patrick Ventrell said, when asked at a press briefing if Washington would appoint Rodman as a US envoy to Pyongyang.

On Sunday, Rodman defended his trip to North Korea, saying regime leader Kim Jong Un does not want war but would like a call from US President Barack Obama.

The colourful Hall of Famer, who won NBA championships with the Chicago Bulls, has become the most high-profile American to meet personally with Kim.

He even appears to have solved one of the mysteries surrounding Kim - his age - telling ABC during an interview that the North Korean leader was 28 years old. So far most experts were only able to say he was in his late 20s.

Ventrell repeated the official US line about the trip, saying: "Dennis Rodman has never been a player in our diplomacy. He does not represent the views of the United States." "We have direct channels of communications with the DPRK. They know how to get in touch with us," Ventrell insisted.

"Instead of spending their money on staging sporting events, the North Korean regime should focus on the well-being of its people, and it should come in line with its international obligations."

"Quite frankly, North Korean words and stunts such as this have no meaning." Rodman - wearing dark glasses, nose and lip rings, and a jacket emblazoned with US money - insisted to ABC that so-called "basketball diplomacy" could be a way to bridge the divide between Washington and Pyongyang.

"He loves basketball. And I said Obama loves basketball. Let's start there, all right. Start there," Rodman said.

Ventrell said if Rodman wants to share impressions of his visit he should call US officials.

The United States and North Korea have no official diplomatic relations, but have kept a channel of communications open at the United Nations in New York, and Sweden also acts as a go-between for the two nations.