The Italian side will confirm the permanent transfer of the Chilean star on Thursday
The Chilean has spent this season on loan with the Serie A side, scoring four goals across 29 appearances for Inter.
Sanchez was recently named to the club’s Europa League squad for the final knockout round games, including Wednesday’s clash with Getafe, as negotiations continued between Inter and Man Utd.
And now, Marotta says that Sanchez’s stay will be extended with the club set to make the announcement shortly.
“Unofficially, we’ll make it official tomorrow morning, the player is entirely owned by Inter,” Marotta said on Sky Sports. “We have a contract with him for three seasons. We believe in him, that he can be a strong part of this squad and are happy to have concluded this deal.”
The signing of Sanchez comes in the wake of some club controversy, with Antonio Conte recently stating that the club gave him and his players “zero protection” during the season.
Marrotta has since stated that the Italian manager’s “work has made itself felt”, with the Inter CEO reiterating on Wednesday that the club is backing Conte.
“We are all very concentrated on this evening, which is an important match. Conte gave a very clear statement yesterday and we refer you to that,” said Marotta.
“Anyone in the football world knows that these dynamics exist and we have to live with this way of doing things. This is an important evening for the future of Inter.
“The owners spoke to Conte yesterday and we all want the same thing, which is to achieve great objectives and make the fans happy.”
He added: “As I’ve said, I honestly just want to focus on this evening. In a larger analysis of a growth process and plan for a new era, with Steven Zhang taking over as president only last year too, these dynamics happen. There are also some objective results that show how we’ve developed.
“We are happy, but want to keep going, improving and reaching even higher objectives. I heard when we stepped into the stadium tonight that we are the vice-champions of Italy, and that really did take me by surprise, but that is what we are and we want to do even better next year.”