Ivan Lendl served 15 aces to complement his strong ground strokes in a 6-1, 7-5 defeat of Bjorn Borg last night in the semifinals of the $250,000 Challenge of Champions tennis tournament.

Lendl's victory put him into Sunday's best-of-five set final against Jimmy Connors. Connors earlier defeated John McEnroe, 6-1, 5-7, 6-2.

In their opening set, Lendl broke Borg's service in each of the second, fourth and sixth games. After Borg won the first game, Lendl collected three aces in the sixth game and then forced Borg to hit three balls into the net.

In the second set, Lendl moved in front 5-2, scoring his 12th and 13th aces of the match.

But Borg regained his strength, holding service in the eighth game and then breaking Lendl's service in the ninth game to trail 5-4.

After Borg held his own service in the 10th game, collecting two aces to square the set at five games each, Lendl went on the attack. Lendl went ahead 6-5, closing out the 11th game with his 15th ace.

In the 12th and final game, the score went to deuce four times before Lendl ended the match by smashing a forehand over the net that struck Borg's racquet and bounced over his head.

While McEnroe, the world's top-ranked player, dodged a match point in the second set and won the battle of aces, 5-0, he was unable to return Connors' service with authority and paid the price.

Connors, meanwhile, used his return of service effectively, keeping McEnroe on the baseline and punishing his younger opponent frequently on forays into the net.

Connors captured the opening set with ease, alternately kicking his service wide to the forehand and going down the center line with pace. He broke McEnroe in the first, fifth and seventh games, yielding just four points on his own service en route to a fast 6-1 decision.

McEnroe handled Connors' opening service of the next set, but was no more successful trying to hold his own.