On Friday, Bayern Munich confirmed they have begun talks with Hoffenheim over a move for Wagner.
Earlier in the week Nagelsmann said the Germany international striker desires a move to Munich, his childhood club.
But Nagelsmann has insisted that a move to Bayern isn't a foregone conclusion for the striker.
"We are open for negotiations but it will depend on the transfer fee," Nagelsmann told Sky.
"We do not have to improve our negotiating position, we're not under pressure and do not have to sell."
The 29-year-old came up through Bayern's youth academy but failed to secure a first-team position before moving on in a career that has seen stops at several different German clubs.
With Bayern in the market for a second striker to help support Robert Lewandowski, the club have begun negotiations for the Hoffenheim forward.
'We have met with (Hoffenheim sporting director) Alexander Rosenand [and] talked about a transfer," Bayern sporting director Hasan Salihamidzic told Sky.
"Of course it will depend on the transfer fee. We are relaxed and don't have too much pressure."
Wagner has scored six goals in 16 appearances in all competitions for Hoffenheim this season.