The silky attacker – who missed the World Cup through injury – rejected a new contract at the Westfalenstadion recently, further fuelling speculation that he may be on the move.
United have been heavily linked with the 25-year-old for some time, while Liverpool are a new name in the mix after selling Luis Suarez to Barcelona.
As well as this a host of clubs from across Europe are said to be watching Reus, who has been one of the Bundesliga’s best players over the course of the last few seasons.
The versatile forward has a reported buyout clause of around £27m in his contract and Rummenigge believes that with his decision to opt against penning a new deal, Dortmund will find it very difficult to keep him:
“I think that it is hard for Borussia Dortmund,” he is quoted by Goal.
“Europe’s top clubs will be very interested to find out Reus’ buyout clause [after he rejected a new contract] as the player is in high demand from a lot of big clubs.”