Riesgo, 26, was a Spain Under-21 international and spent last season on loan at Recreativo Huelva before returning to Segunda Division club Sociedad.

Redknapp needs cover for first-choice goalkeeper Heurelho Gomes because Carlo Cudicini suffered injuries to his pelvis and wrists in a motorcycle accident and is expected to miss the rest of the campaign.

"Asier will train next week with Tottenham," read a statement from Sociedad.

Redknapp will be expected to make a decision on whether he wants to sign Riesgo but no fee has been agreed between the two clubs at the moment.

The Spurs boss is also in the market for a central midfielder to compete with Wilson Palacios, Jermaine Jenas and Tom Huddlestone for a starting place, with Brazilian prospect Sandro a target from Internacional.

Redknapp is reluctant, however, to look for another centre-back despite injuries to Ledley King and Jonathan Woodgate.

"If Woody is fit and Ledley is fit we're great there," he said.

"We're in great shape if they're fit but it's a big if.

"When they played together last year they were a great partnership. But getting them out on the pitch at the same time has proved more difficult."