Gremio director Adalberto Preis has said big-money offers for star players Luan and Walace are expected in January.
Paris Saint-Germain have been linked with striker Luan, while midfielder Walace is also reportedly attracting interest from a number of clubs.
Speaking with Lance! in Brazil, Preis conceded that the Porto Alegre giants will soon be in no position to reject bids for the pair.
"This is not a secret to anybody -- Luan and Walace interest everyone," Preis said. "Gremio have made huge efforts to keep them both up until now but significant offers are coming.
"When I say significant, I mean neither the players nor the club will be able to refuse. We are not a selling club but it is impossible to resist the financial conditions offered by foreign clubs."
PSG director of football Patrick Kluivert has already promised the French champions will be active in January and a striker to back up the in-form Edinson Cavani is thought to be a priority, with River Plate's Lucas Alario one of the names linked with a move to Paris.
Luan is another player reportedly of interest to the Ligue 1 giants, while Wolfsburg's Julian Draxler is also said to be in talks with the capital club.