According to Sky sources, Celtic made an offer in the region of £900,000 for Ciftci and assistant manager John Collins confirmed the club were interested in signing the 23-year-old.
Sky sources also revealed that Wigan Athletic had agreed a fee in excess of £1m for the player, who has one year remaining on his contract at Tannadice.
And although McNamara said he would prefer not to see the striker line up in Celtic’s colours next season, he conceded the decision would rest with the player should United accept a fee from the Scottish champions.
Speaking to Sky Sports News HQ, he said: “It’s out of my hands; everything will always depend on the player if the club accepts a fee.
“Obviously he is going into his last season so that’s the difficult part from the club’s point of view. For me obviously I’d like to keep him but for the lad himself it will always come down to what the player wants to do.
“I don’t think it’s for me to pick and choose (where Ciftci plays next season), as I said it’s down to the player. Obviously you don’t want old players playing against you because we took Nadir two years ago and we’ve worked really hard with him.
“We took him on trial and have turned him into a top-class player so obviously the last thing we want is him is playing against us, but that’s up to the player and we’ll see what his preference is and whether he leaves now or next summer.”
Ciftci, who has been capped at U17 level by the Netherlands and by Turkey at U19s, scored 16 goals in 42 appearances for United last season and has had spells at NAC Breda, Kayserispor and Portsmouth.