Lazio defender Bastos is at the centre of an all-Turkish bidding war between Besiktas and Istanbul Basaksehir.
While over the last couple of days it was reported that Istanbul Basaksehir were the favourites for his signature, Sky Sport Italia report that has now changed.
Besiktas came forward with an improved offer for the 29-year-old.
Fenerbahce had also been linked, but seem to have pulled out of the negotiations.
Angola international Bastos has just one year left on his Lazio contract and joined the club in 2016 from Rostov.
He made 22 competitive appearances for the club last season, scoring three goals and providing one assist.
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