The Spain international has been linked with a move to Spanish giants Real Madrid.
He told the club’s official website: “It’s very clear, Xabi has three years left and we do not want to sell him.”
Assistant manager Sammy Lee added: “The talk about Alonso (going to Real Madrid) is pure speculation. You cannot prevent talk.
“But we always want to keep the spine of the team, our very best players. You can’t stop speculation, but we want to keep the core of our squad, the best players, here.
“New players will be brought in. You always want to keep improving on the field compared to what we have done this season.
“There is a platform now to go forward and hopefully win the title, but we have to get the best out of this squad to do it.”