Group E winners England will face Sri Lanka, the Group F runners-up at the Beausejour Stadium here on Thursday.
Meanwhile Group F winners Australia will play Group E runners-up and defending champions Pakistan at the same ground here on Friday.
The World Twenty20 final takes place at the Kensington Oval in Bridgetown, Barbados, on Sunday.
Brief scores
West Indies 105, 19 overs (S Smith 3-20)
Australia, 109-4, 16.2 overs
Australia won by six wickets
Remaining Fixtures
Thu May 13: 1st Semi-Final - England v Sri Lanka
Beausejour Stadium, Gros Islet, St Lucia
Fri May 14: 2nd Semi-Final - Australia v Pakistan
Beausejour Stadium, Gros Islet, St Lucia
Sun May 16: Final - TBC v TBC
Kensington Oval, Bridgetown, Barbados
Copyright AFP (Agence France-Presse), 2010