The 29-year-old, who is the club's top scorer with 18 goals this season, is out of contract next year.
However, manager Martin Jol is hoping to tie the player down to a new three-year deal.
"We are talking to him," said Jol. "At any club, you want to keep your best players so that is what we try hard to do.
"If Clint Dempsey weren't here, we wouldn't be in this position because we have had to rely on him a lot of times to score goals.
"He is here for at least another year, so that is not a big problem. The problem is that we want to keep him here for longer. But the difference is not very big. He has 17 months left and we want to keep him here for the next three years."