The fast bowler was reported for throwing on his England debut last October and forced to remodel his action.

But he returned to take 50 first-class wickets for the fourth successive season, despite missing six matches due to international calls and a hand injury.

"I definitely think Sussex cricket is heading in the right direction, which is why I am prepared to commit myself to the county for the next four years," said Kirtley.

"Our squad is improving all the time and there's no reason why we should not challenge regularly for honours.

Sussex finished sixth in their first season in County Championship Division One last term.

Pakistani spinner Mushtaq Ahmed was their most recent high-profile signing when he agreed to become the club's second overseas player for 2003.

"Signing Mushtaq Ahmed gives an attack capable of competing with any opponent on any surface," Kirtley added.

"And the strength in depth of our squad has steadily got better."