Chelsea are preparing to launch a final bid of £40 million for Wayne Rooney within the next two days, according to various reports in the British media.
Jose Mourinho has made it clear that he sees Rooney as the missing piece in his squad, and wants him to lead Chelsea's attack. Owner Roman Abramovich is prepared to offer Rooney a four-year deal with wages of £300,000 a week.
Mourinho said after Chelsea's 2-0 victory over Hull: "We will try till the last day to add a new player to the squad, a striker, but in this moment every striker has a club, every striker belongs to somebody and I don't think it's ethical that I name players that belong to other clubs."
"We don't try, like many clubs do, to go around and try to influence players to behave in a certain way.
"If we have to make a bid, we make it in an official way, we don't speak to players, we speak to clubs."
However, David Moyes remains adamant he will not sell Rooney, who provided two assists in United's 4-1 win at Swansea after coming on for Ryan Giggs in the 62nd minute.
And if Chelsea cannot change United's stance, they are set to switch their attentions from Rooney to Robert Lewandowski, the Borussia Dortmund striker.
Lewandowski has one year remaining on his contract at Dortmund, who blocked the striker's attempts to emulate Mario Gotze in leaving this summer for Bayern Munich.
However, Chelsea are hopeful of securing their first-choice target. The club believe the bumper fee will convince United owners the Glazer family that it is in their best interests to sell Rooney.
The Glazers would be unlikely to command such a high fee for Rooney after the transfer window closes as he has just two years left on his contract.
Mourinho is believed to be desperate to land Rooney, but Chelsea think Dortmund would definitely sell Lewandowski at the same price -- and would much prefer to see him leave for England than to join rivals Bayern, who defeated them in last season's Champions League final, for free next summer. Lewandowski would have to be persuaded to leave Germany, though.
Samuel Eto'o, who won the treble under Mourinho at Inter Milan in 2010, is also being considered by Chelsea as a short-term solution up top.
Information from the Press Association was used in this report.