The Chile midfielder has scored four goals in 31 appearances for the Italian side.
Manchester United coach Ole Gunnar Solskjaer said on Wednesday Alexis Sanchez's move to Inter Milan had been made permanent.
Chile midfielder Sanchez, 31, who joined Inter last August after a season and a half at Old Trafford, has scored four goals in 31 appearances for the Italian side.
"I can confirm that Alexis will be confirmed as an Inter player on Thursday," Solskjaer told broadcaster BT Sport.
"Alexis has had a good time over there, he's a good player, so we wish him all the best," he added.
Inter coach Antonio Conte praised Sanchez's impact despite missing more than two months of action earlier this season with a foot problem.
"I think the Alexis Sanchez move is a great one made by the club. Considering the conditions we managed to get Alexis, it was a really good transfer," he told Sky Sport Italia.
"He had come off two years when he was really struggling at Manchester United, then he got this injury with us and we took the time to get him back on track, so it's only right that we are now able to reap the rewards of that effort," he added.
Earlier, Inter chief executive Beppe Marotta said Sanchez had signed a three-year deal at the San Siro.