The Tigers take on Arsenal at Wembley on May 17 for the club's first FA Cup final in their 110-year history.
Since securing a place in the final, Hull have taken just one point from three league games, and Bruce has conceded that their poor form is down to thoughts turning to the FA Cup final.
"I've said for the last couple of weeks the most difficult part is to keep everybody focused," Bruce told reporters.
"The whole city is talking about an FA Cup final and why wouldn't it be. It's been very, very difficult to keep a lid on it because we've still got work to be done.
"It's at the forefront of everybody's mind and it's only human nature that it's something we're all looking forward to."
Hull are currently in 15th place in the Premier League table.