Eddie Dibbs upset John McEnroe and Ivan Lendl reached the final of his 18th straight tennis tournament yesterday in the $500,000 WCT Tournament of Champions at New York's West Side Tennis Club.

Dibbs, overlooked and virtually counted out, took advantage of an aching McEnroe for a 7-6, 6-3 victory. Lendl beat Jose-Luis Clerc, 6-2, 7-5, earlier.

Dibbs, seeded 10th although he is the defending champion, fought off four set points in the opening set and won a controversial tie breaker, 13-11, that was completed in light rain.

The 31-year-old from Miami jumped off to a 3-0 lead in the second set and applied the finishing touch with a break in the sixth game, coming back from 0-40.

McEnroe, the No. 1 player in the world and the top seed in the $300,000 tournament, has had a bad left ankle the past two months and required treatment for it yesterday morning.

Lendl dominated Clerc in the matchup of clay-court specialists in scoring his 88th victory in 91 matches.

Lendl broke Clerc's serve at 15 in the opening game as the Argentinian made numerous unforced errors, as he did throughout the match. In the seventh game, Lendl broke Clerc again at 15. Lendl then served a love game to take the first set.

The two traded service breaks to begin the second set, but Lendl broke Clerc's serve in the third game to take a lead he did not relinquish.

The winner of this champions-only tournament will receive $100,000 and a fur coat valued at $43,000. The runner-up will receive $40,000 . . .

Argentina gained the fourth spot in the World Team Cup semifinals with a 2-1 victory over Australia. The victory earned Argentina a berth against the United States. Australia will meet Spain in today's semifinals.