The 29-year-old left-armer will also be able to take part in the quarter-finals of the competition should Sussex progress to that stage
Sussex have completed the signing of Australia seamer Jason Behrendorff for the final four matches of the T20 Blast group stage.
The 29-year-old left-armer, who took ten wickets for Australia in five matches as they reached the semi-finals of this year's Cricket World Cup, will also be available for the quarter-finals should Sussex progress.
Behrendorff will therefore join compatriot Alex Carey and Australian head coach Jason Gillespie at the club for the 20-over competition.
"I can't wait to be part of the Sharks," Behrendorff said.
"It's a great opportunity and one I feel very fortunate to take on.
"It's been a great tournament so far for Sussex; sitting on top of the southern pool. It's always nice to come into a winning team.
Jason Behrendorff took five wickets against England at Lord's during the World Cup
"I've worked a little bit with Dizzy [Gillespie] before from work he's done with the Australia A side and obviously I've spent a lot of time with Kez [Carey] over the past six months, so I’m looking forward to catching up with them again and meeting the other guys for the first time."
Gillespie himself added: "We felt we just needed something a little extra depth with our bowling now that Tymal [Mills] is injured, Rashid [Khan] has departed and we manage Reece Topley's workload as best we can.
"We're very happy to have Jason fulfilling that role and look forward to him showing what he can do and entertaining our supporters."
Behrendorff is likely to make his debut on Thursday when the T20 Blast returns, with Sussex facing Essex at Hove.
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