The Chelsea player cut inside his marker and scored with a low shot from the edge of the penalty area to break the deadlock in the South American group match after the Ecuador defence had lost possession.

The goal was a relief for Argentina after their opponents had slightly the better of the first half and threatened to pull off an upset.

The visitors had two good efforts before halftime from full-backs Ulises de la Cruz and Neicer Reasco.

Reasco hit the post with a shot from just outside the area and shortly afterwards, de la Cruz had a shot turned away by goalkeeper Pablo Cavallero after he had sneaked between two defenders.

At the end other, defender Gabriel Heinze headed narrowly wide from a corner and Crespo forced a good save from Jose Francisco Cevallos after he broke down the right.

Argentina were missing Inter Milan midfielders Cristian Gonzalez and Javier Zanetti because the match was too close to their club's Italian championship game on Sunday while Juan Sebastian Veron was ruled out with injury.

But the twice world champions livened up after Boca Juniors striker Carlos Tevez replaced Mariano Gonzalez at halftime.

After Crespo's goal, they produced some slick moves in midfield while Andres D'Alessandro provoked the Ecuador defenders with his trickery.

Substitute Juan Riquelme hit the post with a free kick in injury time.

Ecuador's best chance of an equaliser fell to Marlon Ayovi but he miscued and his shot flew high and wide.

Argentina went top of the group with 11 points from five games but have played one game more than Paraguay (9 points) and Brazil (8), who meet in Asuncion on Wednesday.

"We struggled at times but the priority in qualifying matches is securing the three points and we can be happy with that," said Crespo.

Chile won 2-0 in Bolivia with goals from Moises Villarroel and Mark Gonzales in Tuesday's other match to move to fifth in the table.