Anthony Davis had 27 points and 15 rebounds, and Austin Reaves scored 20 points for the top-seeded Lakers, who will face New Orleans on Thursday (Friday in Manila) in Las Vegas.
James put on a masterful shooting performance down the stretch while also racking up 11 assists, eight rebounds and five steals. The 21-year veteran scored 15 of the Lakers' first 19 points in the final period and got the assists on his teammates' other two baskets while Los Angeles pulled ahead.
Kevin Durant scored 31 points, but he badly missed a three-point attempt at the buzzer for the Suns. Phoenix had won eight of 10 before losing to Los Angeles for the third time already this season.
Devin Booker cut the Lakers' lead to 102-101 on a layup with 29 seconds to play, but Reaves drilled his third three-pointer with 15 seconds left.
Bucks 146, Knicks 122
In Milwaukee, Giannis Antetokounmpo had 35 points and 10 assists, Damian Lillard added 28 points, and Milwaukee beat New York to reach the semifinals of the In-Season Tournament.
The Bucks posted a season high in scoring, shooting 60.5 percent (23 of 38) from three-point range and 60.4 percent overall, to set up a matchup with Indiana in Las Vegas on Thursday.
Milwaukee is 5-0 in tournament play and extended its home winning streak to nine games.
Julius Randle scored a season-high 41 points for the Knicks, whose three-game winning streak was snapped. Jalen Brunson added 24 points and R.J. Barrett scored 23 for New York, which earned a wild card berth in the knockout round through a point-differential tiebreaker.