Robert Seguso and Ken Flach defeated Mexico's Jorge Lozano and Fernando Perez Pascal, 5-7, 6-3, 6-4, 6-4, today to give the United States a 2-1 lead in a Davis Cup quarterfinal series.

The United States can clinch the best-of-five series -- and a semifinal berth against Australia -- by winning either of Sunday's singles matches: Tim Mayotte against Mexico's Leonardo Lavalle or Brad Gilbert against Mexico's Francisco Maciel, a first-day winner over Mayotte.

The Mexicans broke the U.S. team's service three times in the first set, with Perez playing aggressively close to the net. But Seguso and Flach rallied in the second set, taking command by twice breaking service.

Australia, inspired by another superb performance from Pat Cash, reached the semifinal by defeating Britain in the doubles to take an invincible 3-0 lead in the best-of-five series in Wimbledon, England.

Cash and partner John Fitzgerald beat Jeremy Bates and Colin Dowdeswell, 6-1, 7-5, 6-4, in 1 hour 35 minutes to clinch a semifinal match at home.

Defending champion Sweden also advanced to the semifinals, beating Italy in Bastad, Sweden. It will play Czechoslovakia, which defeated Yugoslavia.

Sweden is seeking its fourth straight final after losing the 1983 final in Australia and then defeating the United States in 1984 and West Germany last year.

A big crowd had flocked to Wimbledon's No. 1 court at the All England Club to support the British team after the Australians won both of Friday's singles matches in straight sets.

But Britain's chances were dimmed when John Lloyd had to withdraw from the doubles because of a nagging shoulder injury. Lloyd and Dowdeswell had not lost in five Davis Cup matches as a team; Dowdeswell and Bates never had played together in a tournament.

Wimbledon champions Joakin Nystrom and Mats Wilander defeated Paolo Cane and Claudio Panatta, 6-4, 7-5, 6-2, to give Sweden its unbeatable 3-0 lead.