Former NBA star Dennis Rodman lauded North Korea's new ruler as an "awesome kid" and his father and grandfather as "great leaders" at the end of his basketball diplomacy mission to Pyongyang.

At a time of high US-North Korea tensions following Pyongyang's recent nuclear test, the man who once dated Madonna became the most high-profile American to meet Kim Jong-Un, with whom he watched a basketball match.

Kim "is like his grandfather and his father, who are great leaders, he is an awesome kid, very honest and loves his wife so much", China's state-run Xinhua news agency quoted Rodman as saying before he left for Beijing on Friday.

Little is known about Kim's fashionable wife Ri Sol-Ju, who caused quite a stir when she emerged on the national scene last July.

"You have a friend for life," Rodman told Kim in a speech after Thursday's game between a North Korean side and a US team featuring members of the Harlem Globetrotters, which ended in a diplomatic 110-110 tie.

His comments were recorded in a statement by the New York-based VICE media company, which organised Rodman's trip.

Pictures of the event showed Rodman in dark glasses and a baseball cap clapping and laughing next to a clearly delighted Kim, who was dressed in a blue Mao suit with a lapel pin bearing the likeness of his father Kim Jong-Il and grandfather Kim Il-Sung.

The pair were also photographed joking together at a post-game reception, where Rodman, sporting a pink neck scarf and piercings in his nose and lip, appeared to be enjoying a martini.

The Swiss-educated Kim Jong-Un, believed to be aged in his late 20s, is reported to be a huge fan of basketball and the Chicago Bulls, with whom Rodman won three NBA titles alongside Michael Jordan in the 1990s.

While Pyongyang actively promotes the personality cult surrounding the ruling Kim dynasty, many North Koreans remain trapped in poverty and are malnourished or even starving to death, according to aid workers and defectors.

The US State Department, while saying that it took no position on private citizens' travels overseas, disputed Rodman's praise of the Kim dynasty.

"Clearly, you've got the regime spending money to wine and dine foreign visitors when they should be feeding their own people. So this isn't really a time for business as usual" with Pyongyang, acting deputy spokesman Patrick Ventrell said.

"The North Korean regime has a horrific human rights record -- quite possibly the worst human rights situation in the world, depriving their people of food, shelter, water," he added.

North Korea and the United States have never had diplomatic relations.

Rodman's access to Kim, who took over the reins of power after Kim Jong-Il died in December 2011, raised more than a few eyebrows among Pyongyang watchers.

A recent delegation to North Korea that included Google chairman Eric Schmidt and Bill Richardson, a former US ambassador to the United Nations, never got to see the young leader.

Rodman's visit came as the UN Security Council continues to debate how to punish North Korea for carrying out the February 12 nuclear test that triggered global outrage and condemnation.

A day after Rodman arrived in Pyongyang, a state-run North Korean website posted an article warning Washington that the US mainland was "well within" the range of its nuclear weapons.

In an enthusiastic commentary on the Kim-Rodman meeting, the North's official Korean Central News Agency quoted the former Chicago Bulls' star -- nicknamed "The Worm" -- as saying the current impasse in US-North Korean relations was "regrettable".

At a reception after the game, Kim expressed his "pleasure" at the Harlem Globetrotters' visit, and said he hoped such sporting exchanges would improve understanding between Americans and North Koreans.

Rodman tweeted during the visit, to say North Koreans love basketball and that he was "honoured" to represent the United States.

According to the VICE statement, VICE correspondent Ryan Duffy approached Kim during the post-game reception on Thursday and invited him to visit the United States.

"His invitation was met with laughter," the statement said.