NEW YORK (Reuters) - World number one Rafael Nadal was installed as the top men's seed for the U.S. Open on Monday as the Spaniard bids to complete a career grand slam.

Serb Novak Djokovic is seeded third and Briton Andy Murray, the 2008 U.S. Open runner-up, fourth.

Title holder Juan Martin del Potro of Argentina pulled out of the tournament. He is still recovering from surgery on a right wrist injury that has put him out for almost the whole season.

Andy Roddick is the top American, the 2003 U.S. Open winner seeded ninth.

The USTA will announce the women's seeds on Tuesday due to the Monday finish of the rain-delayed Montreal Cup won by world number two Caroline Wozniacki.

The Dane is expected to be the top women's seed after American world number one Serena Williams was ruled out with an injury.

The U.S. Open starts on August 30.

(Writing by Steve Keating in Toronto; editing by Rex Gowar)