French side Lyon have told Chelsea they must increase their £16.75m bid for Ghanaian midfielder Michael Essien if they want to sign him.
Lyon chairman Jean-Michel Aulas has admitted that Chelsea are desperate to capture the 22-year-old this summer.
"Chelsea, who are the only club openly interested in Essien, are putting quite strong pressure on us but we are going to do all we can to keep him," he said.
"We have refused a bid of £16.75m as Essien is worth much, much more."
Essien has been a revelation for the French champions since signing from Bastia two years ago and Aulas believes he is established as one of Europe's finest footballers.
He added: "He is a jewel and one of the best players in Europe. That's why Chelsea are so interested in him but they must put in a price that is worth the best European players.
"I saw that Chelsea had made interesting offers to other players, who are playing with teams on an equal level with Lyon.
"For now, Mickael stays with us, his heart is with Lyon, he wants to stay and we hope he will be with us next season."
Meanwhile, Barcelona striker Samuel Eto'o has revealed that he rejected an approach from Chelsea.
The Cameroonian will instead sign a new contract at the Nou Camp and he said: "I had an offer from Chelsea but I was always clear I wanted to stay at Barca.
"The most important thing is not money. My wife put her foot down over the idea of going to a city like London and I have to respect her for that."
Barca president Joan Laporta said: "For me, he is the world's best striker."