The 31-year-old has spent the entire 2019-20 campaign at San Siro, where he has struggled to make an impact as an ankle injury has limited him to only 15 appearances across all competitions.
Inter have reportedly already decided against making the deal permanent at the end of the season, meaning that Sanchez will return to Old Trafford when his loan period ends.
The Chilean has not featured for his parent club since May, but talkSPORT reports that United will still be forced to pay him £1.1m as part of an annual agreement in his deal.
Sanchez is already understood to be earning £505,000 per week, with only half of his basic salary being covered by Inter during his loan spell.
United boss Ole Gunnar Solskjaer has hinted that the former Arsenal attacker could still have a future at the club when he does return, despite scoring only five goals in 45 games since joining from the Gunners. body check tags ::