The coach insisted that the Brazilian's presence at the club will not change his plans for the France international, who had threatened to leave if PSG signed another defender
The Brazil international completed his move to the French capital earlier on Saturday for a reported fee of €42 million.
Sakho, who featured sporadically for PSG since Ancelotti took over the team, has threatened in the past to leave the club, should another defender arrive at Parc des Princes.
The coach, however, has moved quickly to dismiss the notion that the France international is surplus to requirements, and stated that he would like to see the centre-back remain in Paris.
"With [Thiago] Silva and Alex, we have good central defenders and I will choose the best possible option for each game. I will not forget the other defenders who train hard," Ancelotti told AFP.
"I will not talk about a player who leaves the club in a stand-off. Sakho may request to move, but our decision is that we want him to stay."
The coach then took time to praise the new arrival, saying that Thiago Silva will make a big impact at the club.
"He is a fantastic player. Everyone knows he is one of the best defenders in the world. I'm very happy. It will improve the quality of the team. The club has done a fantastic job. It was not easy to take a player like him."
Thiago Silva will join his new club in late August after the Olympics in London, where he will represent Brazil.