The 32-year-old defender's deal expires next summer, but his representatives are in negotiations with the Championship club.
Shittu, who joined Millwall from Queens Park Rangers in 2012, has made it clear that he wants to remain with the London outfit.
"I love it here, I love everything about it," he told the London Evening Standard.
"They need to be happy and I need to be happy but I am trying to commit my future to Millwall because they've done a lot for me. Hopefully we can get it sorted and I can stay for the next couple of seasons.
"I have been linked with a few other clubs but that is not important to me because I want to be at Millwall. I adore the fans and our manager believes in me."
Shittu has made 40 appearances for Millwall this season in all competitions.