Bayern Munich manager Julian Nagelsmann said on Sunday that Borussia Moenchengladbach were "playing poker" over the possible winter transfer of goalkeeper Yann Sommer to the German champions.
Bayern have looked to Sommer as an immediate replacement for injured captain Manuel Neuer.
Neuer broke his leg while skiing in December and will miss the remainder of the Bundesliga season, along with much of 2023.
On Saturday, Gladbach sporting director Roland Virkus told Germany's RP Online "we will not give Yann Sommer up. We also told Bayern that".
Sommer, who is also the first-choice 'keeper for the Swiss national side, has long been one of the best in the Bundesliga and could be available on the cheap due because his contract expires in the summer of 2023.
While telling the press on Sunday from Bayern's winter training camp in Doha that he "does not read the news", Bayern coach Julian Nagelsmann said he felt Gladbach were stonewalling the move.
"I think it's part of the job that you (Virkus) put on a poker face in this area," Nagelsmann said.
"For us, the situation is very challenging.
"We are looking at what's going on in the transfer market."
The Bayern coach said Neuer's freak injury was "tragic" but added that he backed No 2 'keeper Sven Ulreich for the remainder of the season.
"If we can't do anything, I'm also very confident that we will play a very good second part of the season."
Bayern, who are four points clear at the top of the Bundesliga, re-start their season away at third-placed RB Leipzig on 20 January.