The Londoners are planning to make a £25milion offer for the England striker in the coming days after their initial £20m bid was turned down.

It is understood Chelsea are prepared to spend up to £30m to secure the services of the disgruntled United veteran.

"The club are working hard to keep the numbers in balance but we can still invest in a player who costs £20m, £25m, £30m and not break the balance," Mourinho was quoted as saying by the English press.

"We don't need to sell to do that."

Asked if he could spend £50m on a striker, Mourinho said: "The striker I want doesn't cost £50m."

While Mourinho insists Chelsea will not need to sell should they sign Rooney, one of Demba Ba or Fernando Torres are expected to leave should the United star join.

Rooney's relationship with departed manager Sir Alex Ferguson became strained last season.

New boss David Moyes, who gave Rooney his English Premier League debut as a teenager with Everton, has attempted to restore the 27-year-old's faith in the club.

However, United chief executive Ed Woodward says the reigning Premier League champions are in no rush to offer Rooney a new deal.

His current contract expires in June 2015.

It is understood Chelsea are prepared to match Rooney's £220,000-a-week wages and are planning to offer him a four-year deal.

The two clubs are scheduled to square off at Old Trafford on August 26 and a deal is not expected to be done before that clash.