Ecuador took a 1-0 lead over the United States today on the opening day of Davis Cup tennis competition when Andres Gomez defeated Jimmy Arias, 7-5, 4-6, 4-6, 9-7, 6-4, in 4 1/2 hours.

The match, before 6,000 at Francisco Segura Cano stadium, opened the five-match series.

In the second match, Aaron Krickstein led Ecuador's Raul Viver, 8-6, 6-1, 2-2. They are scheduled to resume at 11 a.m. EST Saturday. The doubles match between the Americans Ken Flac and Robert Seguso and Gomez-Raul Ycaza is set for 1 p.m.

Gomez, who won the first set with ease, seemed surprised by Arias' quick moves and good shot placement as Arias won the second and third sets. He was on the verge of taking the match in the fourth, when Gomez turned things around.

In the final set, both players broke serve five times. Gomez took a 4-2 advantage, but Arias came back for a 5-4 lead. Gomez won the match by breaking Arias' serve in the last game.

"It was a difficult match, due to the heat and humidity that affected us both," Gomez said.

In other Davis Cup action today:

Boris Becker defeated Mexican Leonardo Lavalle, 6-3, 6-2, 6-4, in Mexico City to give West Germany at 1-0 lead.

Becker dominated from beginning to end and only fell behind early in the third set, when Lavalle broke his serve in the fourth game for a 3-1 advantage. But Becker broke Lavalle's serve in the fifth game.

The winning team plays the U.S.-Ecuador winner.

Glenn Michibata defeated Ricardo Acuna, 6-3, 6-3, 4-6, 8-6, to give Canada a 1-1 tie with Chile; Peru took an insurmountable, 3-0 lead over Colombia in a series begun Thursday; Martin Jaite's win over Marcelo Filippini, 6-4, 6-4, 6-2, helped Argentina to a 2-0 lead over Uruguay; Sweden led Denmark, 2-0, after Mats Wilander beat Morten Christensen, 8-6, 6-2, 10-8; Italy led Paraguay, 1-0, with the match between Claudio Panatta and Victor Pecci suspended by darkness.