Bayer Leverkusen on the verge of historic double after reaching ...

Bayer Leverkusen is on the verge of a historic league and cup double in Germany after sweeping aside local rival Fortuna Duesseldorf 4-0 in the German Cup semifinals.

Florian Wirtz scored twice on Wednesday as Xabi Alonso's team, which also leads the Bundesliga by 13 points, marked its 40th game of the season unbeaten in all competitions.

Leverkusen faces off in the May 25 cup final at Berlin's Olympiastadion against second-tier Kaiserslautern, which ended the surprise run of third-division Saarbruecken with a 2-0 win on Tuesday.

On a wet night, Leverkusen took the lead in the seventh minute when Jeremie Frimpong seized on a loose ball at the far post and lofted a shot over goalkeeper Florian Kastenmeier.

That forced Fortuna to open up its play in search of a goal, and Leverkusen promptly responded with a searing counterattack.

Three passes took the ball from Leverkusen's touchline to the back of Fortuna's net as Amine Adli made it 2-0. Soon it was three as Kastenmeier gave the ball away to Leverkusen midfielder Robert Andrich, who set up Wirtz to score.

Wirtz scored another from the penalty spot after a handball, before Leverkusen celebrated the return of striker Victor Boniface, back in action for the club for the first time since December after he was injured while training with Nigeria ahead of the Africa Cup of Nations.

Leverkusen had a further boost last week when Alonso said he would stay on as coach amid speculation linking him with Liverpool and Bayern Munich. Since then, Leverkusen has won both its games and seen Bayern coach Thomas Tuchel concede the Bundesliga title race.

Fortuna, which is pushing for promotion from the second division, was a heavy underdog ahead of the game, even before its star midfielder Ao Tanaka was ruled out.

The Japan international had to go into urgent surgery to remove his appendix and gave his teammates a pregame thumbs-up gesture from a hospital bed.