Singapore (AFP) - Former US basketball star Dennis Rodman flew into Singapore late Monday ahead of at summit betwen President Donald Trump and North Korea's Kim Jong Un, playing down expectations of an immediate breakthrough at the historic meeting.

Rodman, who has struck up an unlikely friendship with the basketball loving North Korean leader, arrived in the city-state some nine hours before Trump meets with Kim in a bid to negotiate an end to a decades-old nuclear stand-off.

He said he expected the Trump-Kim summit to "go fairly well" but added "people should not expect too much for the first time".

"I'm just happy to be a part of it," he told reporters at Changi Airport.

"I think that I brought awareness to a lot of things around the world and I think North Korea has given a lot of people the opportunity to do this conference now and I hope it's a success.

"Who knew this would have happened five to six years ago... It's exciting to be a part of it."

Rodman, sporting a black t-shirt advertising a cryptocurrency he is involved with, said he was unsure whether he would get to meet with Kim -- a man he has previously described as a "friend for life".

"Every time I see him it's always a surprise. So maybe tomorrow it's the same thing. Maybe it's a surprise I'll see him tomorrow before he leaves," he said.

Rodman has made five trips to Pyongyang since Kim took power.