The Manchester rivals are reportedly battling it out for the 29-year-old's signature, despite being able to pick up him on a free contract at the end of the campaign.
United's rumoured interest in Sanchez, which could see Henrikh Mkhitaryan head the opposite way, may have complicated things for the Gunners as they were initially determined to keep their star man until the summer.
According to Wenger, though, it remains to be seen whether the Chilean will still be at the Emirates Stadium come the start of February.
"Look, honestly, I cannot tell you much more at the moment about this situation," he told reporters. "Nothing is really concrete. I don't want to give you wrong information. Nothing is decided one way or another.
"It is always beneficial to the club who can take advantage. But we are not in that. Normally you should stay until the end of the season but we will see."
Sanchez has yet to hit the heights of last season in an Arsenal shirt, but he has still managed seven goals and three assists in 19 Premier League outings.