Boston: The Boston Celtics rode the outside shooting of Paul Pierce and a superior inside game to beat the Los Angeles Lakers 92-86 in the NBA Finals on Sunday and move within one victory of a record 18th championship.

Pierce had 27 points, mostly from long range, to help send the Celtics to Los Angeles for Game Six today with a 3-2 lead in the best-of-seven series.

"This was huge for us," Celtics coach Doc Rivers told reporters. "Let's just be honest. We had to win this game, and that's the way we felt going into it. For them they still have two home games, and they understand that."

Should the Lakers win Game Six, the winner-take-all series finale between the league's most celebrated franchises will also be in Los Angeles, on Thursday.

"You don't want to go into LA down 3-2 with two games in LA," Pierce said. "So this was the biggest game of the year. Every game gets bigger. Great opportunity for us — got two games in LA, we've just got to get one. We've been a great road team all year. We're just going to try to get it done."

Kobe Bryant scored 38 points but the Los Angeles guard received little support, Spanish forward Pau Gasol adding just 12 as the only other Laker to reach double figures.

The Celtics once again dominated under the basket and connected on 56 per cent of their shots while the Lakers made just 39.7 per cent.

Lakers guard Bryant scored his team's first 19 points of the second half on seven-of-nine shooting, including all three of his shots from beyond the arc.

But Boston refused to fold, turning a six-point lead at intermission into a 73-65 advantage with one quarter left to play.

"He was shooting fadeaway threes, fadeaway jumpers off the double team," Pierce said of Bryant.

"You knew he was going to come out and be aggressive and try to carry his team. Kobe is the one guy that you probably can't stop in this league, but we feel like with these other guys we can slow them down and give ourselves a great chance at winning."

Bryant finished with 13 of 27 shooting, including four of 10 from three-point range, five rebounds and four assists.

Despite Bryant's third-quarter heroics, the Lakers were unable to trim their deficit because the Celtics hit 12 of 19 shots.

"Defensively were weren't very good at all," said Bryant.