Reports in Mexico claim that the best offer is from the Upton Park club and they are now in pole position to claim his signature.
"We don't want to be making announcements when it's not the correct moment. When everything is OK we will make an announcement," said Pumas director of sport Mario Trejo.
"It's very possible that between Thursday and Friday we will have something more serious to say.
"If there is an important announcement to be made, the president will be in charge of letting everyone know.
"We can't talk too much about it because then everything gets complicated and as we are very near to reaching an agreement we don't want to spoil the negotiations."