Sigurdsson scored nine times and registered 13 assists in 38 Premier League appearances for Swansea last season, while Llorente scored 15 times in England's top flight following a move from Sevilla last summer.
Both players have been linked with transfers away from the Liberty Stadium ahead of the 2017-18 campaign, but Jenkins has stated that he has received 'no firm bids' for either.
"We've not had any firm bids and if we ever get any firm bids then we will deal with them in the proper way," Jenkins told Sky Sports News. "Our aim is to try and keep Gylfi and Fernando, keep our better players and to make sure we can add to Paul's [Clement] squad.
"It's hard to suggest what sort of value Gylfi has in today's market, but to us he is priceless and we've got to make sure we do everything in our power to make sure he stays with us."
Everton have been credited with an interest in Sigurdsson, while Chelsea were strongly linked with a mid-season swoop for Llorente.