The 27-year-old winger is currently on loan at the Potters from the Spanish side until January 2011.
"He's a good lad, he's been very good for us but whether we can do a deal or not remains to be seen," Pulis told BBC Radio Stoke.
"You're dealing with a Spanish club, it's not cut and dried where I can ring up a manager and speak to them and understand where the kid stands," he said.
"You're dealing with a club who might deal differently than what we do."
Chief executive Tony Scholes echoed Pulis' concerns but said the club will persevere.
"It's something we're looking at very closely at the moment," he said.
"Whether or not there's an opportunity depends on the club he's permanently registered with and it also depends where Jermaine himself sees his future.
"But given the form Jermaine's in at the moment, I think it's one our supporters would like us to do everything we can on."