Reus, 24, joined Dortmund in 2012 and has a market value of €34 million, according to Transfermarkt.
As of Dec. 18, the German international had scored eight goals and contributed five assists in the league this season, per WhoScored.
Keep checking back here for the latest news and rumours on Reus throughout the week.
Updated Jan. 2
Kent wrote that Reus, who is reportedly United manager David Moyes' "main transfer target," will cost "up to £40 million."
German newspaper Bild reported (via Goal.com) in January 2012 that Reus' contract included a €35 million release clause that would take effect in 2015.
The report also mentioned a similar clause—quoted at £29.4 million—in the Reus contract, but also claimed that this "situation has changed" following Mario Goetze's move from Dortmund to Bayern Munich this past summer.
Marco Reus reportedly has ruled out a January transfer, according to quotes attributed to him in German newspaper Bild.
Speaking to Bild (as translated and cited by Goal.com), Reus said: "I have a contract with Borussia Dortmund and I am happy to be here."
He added: "All I can say about is that I am not thinking about a transfer. I am focused on BVB and anything else is something for the future."
The Goal.com article mentions Manchester City and Barcelona as potential suitors for Reus.