The first legs will take place on April 26 with the second on May 3.
Atletico Madrid have confirmed that Diego Costa suffered a hamstring injury in Thursday's Europa League match against Sporting CP.
The tie will mark a first European semi-final in nine years for Arsenal and they will be hoping for another year of silverware success after a disappointing domestic campaign.
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With Arsenal themselves likely to miss out on the top four, winning the competition is their best chance of playing Champions League football next season.
Diego Simeone's side are now second in LaLiga behind runaway leaders Barcelona.
Koke said he would give Jan Oblak a blank cheque to ensure he remains at Atlético Madrid after lauding the goalkeeper's performance in the Europa League. They are in first place in the Austrian Bundesliga, but the victor only gets a spot in the Champions League playoffs.
French club Marseille will play Red Bull Salzburg in the other semifinal.
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The Gunners came from 2-0 down to draw the second leg of their quarter-final at CSKA Moscow 2-2 on Thursday night, progressing 6-3 on aggregate against the Russian side. Meanwhile, their rival knocked out CSKA Moscow, Lazio, RB Leipzig to qualify for the current stage of the competition.
Now, this is a tournament that means much more to Arsenal, Marseille and Red Bull Salzburg when it comes to next season.
Extra incentive for Marseille - the final is in Lyon, France.
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