Arsenal manager Arsene Wenger has denied reports suggesting the club are poised to sign Jonny Evans but says the club are trying to to bring new players in.
Arsenal would be willing to sell Sanchez for a fee no less than £35m provided they are able to sign Riyad Mahrez as replacement.
The north London club are looking to bolster their defence having conceded eight goals in their last four league games.
Tarkowski recently signed a new long-term contract at Turf Moor but has been linked with moves to Arsenal and Manchester City.
City were close to completing a deal for Sanchez last summer but the Gunners backed out after being unable to find a replacement.
Spaniard returned to action on Tuesday after missing two games and took to Twitter to explain his absence.
Sanchez is in the final knockings of his contract in north London and has been courted by Manchester City for a number of months.
Sanchez is in the final six months of his contract at the Emirates Stadium and is widely expected to leave the Gunners.
Chelsea manager Antonio Conte has revealed that he is a huge fan of Chilean duo Arturo Vidal and Alexis Sanchez ahead of their game against Arsenal at the Emirates.
Manchester City will hope to finally conclude a deal for Alexis Sanchez in January as they eye further reinforcements to their squad.
Samuel Umtiti is contracted to Barcelona until the summer of 2021 but has a £50m release clause which can be triggered by interested clubs.
Antonio Conte should be given big transfer funds to strengthen several areas of his Chelsea squad during the January transfer window.
Alexis Sanchez has long been linked with a move to Manchester City. After a failed move, the Chilean international is likely to join Pep Guardiola's side in the summer.
Virgil van Dijk was heavily linked with a move to Liverpool in the summer transfer window. The Dutch international had to wait for few months before completing Anfield switch.
Gabriel Jesus will be out for over a month but Kevin de Bruyne could return earlier despite being stretchered off late in the game against the Eagles.
Wilfried Zaha was believed to be valued around £40m. The Ivory Coast international is a transfer target for Manchester City, Arsenal and Chelsea.
Thierry Henry wants Arsenal to sell Mesut Ozil and Alexis Sanchez in January as they would be available to move out on a free transfer in the summer.
The Red Devils are 15 points behind bitter rivals Manchester City, while they were also knocked out of the Carabao Cup by Bristol City last week.
Raheem Sterling's 17th goal of the season is the difference as profligate Manchester City deservedly beat Newcastle 1-0 at St James' Park.
Jack Wilshere will enter the final six months of his Arsenal contract in January. Giroud and Sanchez have been linked with moves away from Arsenal.
An alternative review of football in 2017 featuring Rod Stewart, referee stag dos and Twitter taking over the summer transfer window.
Manchester United have spent close to £300m since Jose Mourinho took over but the Portuguese coach believes it is not enough to challenge Manchester City.