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The Serie A leaders are looking to bolster their squad in the January transfer window, as they attempt to sustain their title charge under Antonio Conte.
Inter are ahead of Juventus on goal difference alone with 18 games played and they see Vidal - who has won league titles with Barca, Juve, Bayern Munich and Colo-Colo - as the perfect addition going into the second half of the season.
"We'll do something, it's an important moment and we want to keep going," Marotta told reporters.
"Vidal is one of our targets. As for [Tottenham playmaker Christian] Eriksen, the market closes at the end of January.
"We're working hard, but to improve the quality of our squad, important signings are needed and it's for this obvious reason that there are difficulties."
Vidal is widely believed to be keen on leaving Camp Nou during the current transfer window, but Barca manager Ernesto Valverde said he wasn't considering any potential exit.
"We're not thinking about him going to another team," he told a press conference before Barca's 3-2 Supercopa defeat to Atletico Madrid on Thursday.
"We'll see tomorrow [Thursday]. In principle he's with us. No clues.
"Arturo Vidal plays for us... we don't pay any attention to other clubs being interested in our players."
The Chilean came off the bench at half-time with his side 1-0 down, and scored what had looked to be the winning goal before Wu Lei's last-gasp equaliser.
"There's a lot of speculation right now, we're all active," Marotta added.
"Generally speaking, you all know very well that you can do tonight what you don't do today."
Inter vice-president Javier Zanetti has said he believes the signing of Vidal would take his side up a level.
Inter's next fixture sees them host Serie A's top-scoring team, Gian Piero Gasperini's Atalanta, on Saturday.