The 21-year-old defender has just returned to Stamford Bridge after spending the second half of last season on loan at Middlesbrough.
Omeruo impressed hugely at the Riverside and Boro boss Aitor Karanka has already confirmed his interest in bringing him back.
However, Omeruo first needs to resolve his Chelsea future with just 12 months left on his current deal.
Omeruo - who is set to go to the World Cup with Nigeria - has now turned down an initial offer, according to his agent.
Omeruo's adviser Chika Akujobi is quoted by AfricanFootball.com suggesting their proposal is not good enough.
"We want them to double the offer, but they said they have a new policy for young players who have yet to break into their first-team and this ensures they do not go overboard with their offers," he said.
"But Kenneth has already proved himself in the English Championship which is even more forceful and physical than the English Premier League, which is more about tactics.
"Chelsea have to come up and they have to do so soon, before the club go on summer holidays."