Manchester United boss Louis van Gaal has been told money is no barrier if he wants to improve his squad.
Van Gaal spent £150m in the summer, including a British record £59.7m on Angel Di Maria, but still trail Chelsea by 11 points in the Premier League.
Defensive midfielder Kevin Strootman and defenders Mats Hummels and Diego Godin are all targets for United.
However, United chief executive Ed Woodward has already said any "short-term fixes" in January are unlikely.
Speaking last month, he revealed: "We have targets we are looking at for next summer.
"Should any of them become available in January, which is obviously rare, we will consider acting. But it is a low probability."
United sources question whether Roma would allow Dutch international Strootman, 24, to leave when they are still battling for the Serie A title.
|All of Manchester United's six major summer signings - Ander Herrera, Luke Shaw, Marcos Rojo, Angel Di Maria, Daley Blind and Radamel Falcao - have had spells out injured this season|
Similarly, Borussia Dortmund would probably be reluctant to release Hummels, 25, with the club in a surprise relegation battle.
As for 28-year-old Godin, his Atletico Madrid team still have a chance of retaining La Liga and remain in the Champions League.
With fourth-placed United targeting a spot in next season's Champions League and with their commercial arm continuing to raise huge sums, Van Gaal has been told he can eclipse last summer's spending.
He will also be allowed to decide the United futures of defenders Rafael, Phil Jones, Chris Smalling, Jonny Evans and striker Robin van Persie, who are all out of contract at the end of the next season.
The club are expected to open talks with goalkeeper David De Gea - he is also out of contract in 2016 - while midfielder Michael Carrick is set to be offered a deal to keep him at the club beyond next summer.
Out-of-favour midfielder Anderson is almost certain to leave, although United have ruled out the option of paying the Brazilian the remainder of his contract to get him out of the club sooner.