Reports in Portuguese publication A Bola suggest the 25-year-old has told his representatives that he is keen on a move to Sporting CP, who are also monitoring the striker's situation.
Celtic have been linked with the Slovenian hitman for some weeks now while Bristol City, Al Gharafa and Dynamo Kiev were also credited with an interest.
Earlier this week, Slovan Bratislava warned the Hoops that they risked missing out on the striker if they didn't move quickly. The club's directors claimed they had turned down one offer from Celtic and wouldn't sell Sporar for anything less than £6 million, although A Bola disputes that the champions ever submitted a concrete offer.
Slovan director Ivan Kmotrik told The Sun: "On December 23, there was a meeting between SK Slovan Bratislava and Celtic FC in the presence of Sporar’s player agent.
“We discussed with Celtic the possibilities for a potential transfer. Celtic responded that they would send an official proposal. But they didn’t make any more calls and didn’t send any proposal after our meeting.
“We don’t know now what the situation is with Celtic’s interest in Sporar. We have received offers from several clubs and we are open to negotiation with all serious partners, including Celtic. However, we will only accept a transfer fee which matches Sporar’s current value.”
The Slovakian side are understood to value Sporar at around £7 million and have reportedly turned down one offer below £4.2 million from Sporting. Reports suggested they were holding out for between £6 million and £7 million but may end up accepting a bid of around £4.7 million.