Sussex have signed Brendon McCullum for the Twenty20 as a replacement for Tillakaratne Dilshan after he was declined permission to play by the Sri Lanka board.

Dilshan had been due to join Dwayne Smith as Sussex's two overseas players for the tournament that starts on June 1, but Sri Lanka have now scheduled tours to USA and Zimbabwe over the same period.

However McCullum, who hit an unbeaten 158 in the opening IPL match three years ago, is a more than decent replacement at the top of the order although is unlikely to be needed with the gloves as Sussex have three keepers - Matt Prior, Andrew Hodd and Ben Brown - on the staff.

"Brendon was always on our short list for 2010 and once New Zealand's tour to Zimbabwe was postponed we made our move," said Mark Robinson, the Sussex cricket manager. "His power at the top of the order can give us the start we need to help us defend our 2009 title success. It is a shame that Sussex supporters will not get to see Dilshan though we hope we can bring him at some point in the future."

Dave Brooks, the chief executive, added: "We are extremely grateful to New Zealand Cricket for their speedy release of Brendon. The international calendar becomes ever more congested, so we understand the difficulties that Cricket Sri Lanka had over Dilshan."