Chelsea are discussing what they consider would be a "knockout" £40m bid to sign Wayne Rooney.
The offer would be vastly higher than their opening bid of under £25m, which was flatly rejected by Manchester United, who insist the unsettled striker is not for sale.
United manager David Moyes and the club's executive vice-chairman, Ed Woodward, maintain that Rooney will stay at the club, but Chelsea are continuing to test that resolve. The timing of the revelation last week that Rooney felt "angry and confused" with life at United was telling, as it came on the day that Chelsea submitted their bid.
Rooney attempted to seize on comments by Moyes about his role in the United team, which were misinterpreted to suggest he was solely understudy to Robin van Persie, to justify his desire to leave.
United have indicated that even if the England international, who has two years left on his current deal, hands in a transfer request he will not be allowed to depart this summer.
While Moyes remains convinced he can persuade him to stay, Alex Ferguson's continuing presence as a club director is understood to be a central issue in Rooney's discontent.
Rooney remains angry at Ferguson's claim that he asked for a transfer during a private meeting between the pair in April – a claim denied by the player's camp.
Rooney is Mourinho's No 1 target and Chelsea are working on the make-up of a revised bid. It may be that they offer add-ons which take its value closer to the £40m figure.
There were claims last week that Chelsea had offered either David Luiz or Juan Mata, plus cash, to try to sign Rooney but this was immediately dismissed by the club. It is understood that Chelsea will make only cash offers for Rooney.
Mourinho also insisted that neither player is for sale but it is likely that Chelsea will receive offers from both Barcelona and PSG for Luiz, who could cost up to £45m.