OL coach Remi Garde is under pressure to sell before he can buy this summer.
But Bernard Lacombe, advisor to club president Jean-Michel Aulas, admitted they could break from that template to move for Sakho.
Big-spending PSG's Qatar-funded programme of squad-building has stepped up this summer and includes the high-profile signing of AC Milan defender Thiago Silva, which could leave France international Sakho surplus to requirements.
"The plan is to sell two players before we start recruiting," Lacombe told L'Equipe.
"But it's true, we at least need one central defender and maybe a defensive midfielder. That is why we are interested in Mamadou Sakho."