England's Lee Westwood and Sweden's Robert Karlsson were engaged in an engrossing battle for the Qatar Masters title on Sunday, after overnight leaders Bradley Dredge and Paul Casey fell way behind on a windless day at the Doha Golf Club.

After 13 holes in the final round, Karlsson was one shot ahead of Westwood on 13-under-par, with Australian Brett Rumford and defending champion Alvaro Quiros four shots off the pace in joint third spot with nine under.

Casey and Dredge failed to take advantage of the benign conditions to slide out of contention.

Casey, who was 10-under overnight, had a nightmarish final round with five bogeys and a double bogey to slip to six-under after 13 holes.

Dredge fared slightly better with two bogeys and a double bogey to be eight-under with five holes to go.

© 2010 AFP/sid