Manchester United and Manchester City will go head-to-head for the signatures of FC Porto duo Eliaquim Mangala and Nicolas Otamendi, according to the Daily Star.
The centre-back pairing - who are valued at a combined £65million - have been heavily linked with Premier League transfers, having attracted interest from a number of different clubs.
Red Devils boss David Moyes is reportedly keen to bring £40million-rated Mangala to Old Trafford when the transfer window reopens in January.
And, it has now emerged that the champions are considering a £25million bid for the France international's Argentine teammate at the turn of the year.
Manchester United chief executive Ed Woodward recently confirmed that Moyes’ transfer priorities were a central defender and a left-back, since succeeding Sir Alex Ferguson as manager during the summer.
If all goes to plan, the arrival of the two Porto stoppers will be supplemented by the signing of long-term target Leighton Baines from Everton, in what will be a significant shake-up of Manchester United's defensive department in the New Year.
However, Moyes will face serious competition from Manuel Pellegrini, particularly in the chase for Otamendi, after Manchester City sent International Recruitment Manager Rob Newman to run the rule over the 25-year-old in last weekend's 3-1 win over Sporting Lisbon.