The San Antonio Spurs have claimed a crucial lead in the NBA Finals by beating the Miami Heat 110-95 in a dramatic opening game of the series.

There was a predictable battle for control in the opening stages of the match as scoring was made to look easy for both sides in a first quarter which San Antonio edged 26-20.

It soon became clear that conditions would play a part inside the AT&T Center, with players and supporters struggling in the heat due to a fault with the air conditioning in the arena.

Miami trailed by just five at the break, and it appeared that the interval would make the difference as the defending champions returned to take charge of the game.

Dwyane Wade played a key role for most of the night, registering 19 points, but it was the entire Heat side who looked a step quicker as the Spurs committed a number of turnovers at vital times to hand the lead to the visitors.

LeBron James, who top-scored for the Heat with 25 points, was forced off the court twice in the final quarter appearing to be battling cramp as the temperature continued to cause problems in Texas.

San Antonio responded to a below-par third quarter in perfect fashion as they went on a 31-9 run in the closing stages to earn the control once again.

Tim Duncan topped the charts with 21 points for San Antonio, while Manu Ginobili contributed 16 points and 11 assists off the bench, but it was a pair of three-point efforts from Danny Green which eventually saw the hosts pull away from their rivals.

Miami were unable to produce a dramatic fightback late on, with the problems suffered by James, who was helped into the locker room, piling on further disappointment on a frustrating evening for Erik Spoelstra's side.

San Antonio will host the Heat once again in game two on Sunday night.