The Football Association has defended its choice of venues for the FA Cup semi-finals amid slow ticket sales.

Watford are reported to have 1,500 tickets left unsold for Saturday's semi-final against Manchester United at Villa Park.

Blackburn and Chelsea, who meet at Old Trafford on Sunday, have both failed to sell 8,000 seats of their allocations.

An FA spokesman said: "Old Trafford and Villa Park are established venues, used to dealing with the logistics."