LAS VEGAS (AFP) — The National Basketball Association's inaugural in-season tournament nears its climax in Las Vegas on Thursday with the world of basketball in near-unanimous agreement that the event has been a dazzling success.

Four years after it first emerged that the NBA was mulling the creation of a 30-team tournament played in tandem with the regular season, four teams will contest in the semifinals, hoping to nail down a place in Saturday's final.

LeBron James and the Los Angeles Lakers face the New Orleans Pelicans in the Western Conference semifinal, while the Milwaukee Bucks face the Indiana Pacers in the Eastern Conference side of the draw.

The Vegas finale marks the culmination of NBA commissioner Adam Silver's desire to see basketball mirror European club football's structure, where teams play in domestic and continental knockout cup competitions as well as league campaigns.

Silver said earlier this year the tournament was designed to "create new games of consequence during the regular season," and in that regard the tournament has been an unqualified hit.

Viewership figures have surged for locally broadcast and nationally televised games, while attendances in November jumped to an average of 18,206 — the highest average on record for November according to the NBA.

"It gives that excitement and that different level of competition and care that you don't usually get in December in an NBA season," Milwaukee Bucks star Damian Lillard said on Wednesday.

"I think it's doing what it's supposed to do. A lot of teams who probably didn't appreciate it in the first one or two In-Season Tournament games are probably wishing like, man, we should have taken this a little more serious."

Lakers coach Darvin Ham agreed, saying the tournament had given a sense of jeopardy to a period of the NBA's marathon 82-game regular season that is traditionally a snooze-fest.

"I think it's been great," Ham said.

"Sometimes, you tend to yawn — we don't like to admit it, but you tend to yawn through certain NBA games, regular-season games at this point of the year."

"To have this infused into the season and you get a chance to see this high level of basketball played in December, I think it's great for the fans, great for everyone involved, great for the league, and just another feather in the cap."

The sense of competition has crucially won buy-in from the NBA's players. Each player on the team that lifts the title on Saturday will receive a win bonus of $500,000, although Ham believes the purse could be bigger.

"If you want the players to play at an extremely high level, increase the purse," Ham replied when asked how he felt the tournament could be improved.

In broad terms, however, the tournament has proven popular with players.

Milwaukee star Giannis Antetokounmpo, who celebrated his 29th birthday on Wednesday, is relishing this week's detour in Vegas.

"I had my birthday in Vegas," Antetokounmpo said.

"That's what I'm going to tell my kids one day. My 29th birthday was in Las Vegas. What were you doing out there, dad? Were you gambling and being in the gentlemen's club? No, I was playing a basketball game."

The Greek star questioned whether any changes needed to be made to the format moving forward.

"I don't think there's anything to tweak," he said.