Lautaro has been tipped to swap Serie A's Inter for La Liga champions Barca, who are determined to sign a long-term replacement for veteran forward Luis Suarez.
Despite Barca's reported interest amid the coronavirus pandemic, Inter sporting director Piero Ausilio insisted Lautaro will not be sold for anything less than his €111 million ($124m) buyout clause.
Asked about Argentina international Lautaro, Moratti told Sportmediaset: "You can't hold someone who has the idea of being somewhere else.
"That would put him in a position to remain involuntarily or, in any case with a different impulse, in the same place."
Though Barcelona has been keen to offer several players as part of a swap deal to drive Lautaro's fee down, Ausilio has drawn a line in the sand and said the exit clause must be met.
"As far as Martinez is concerned, there is only one way that he will leave Inter and that is by paying his clause," Ausilio told Sky Italia, "A clause that everyone knows – there is no point in hiding – is demanding, because it has both deadlines and commitments that must be kept very precise.
"It is a clause that expires in the early part of July so it won't last for a long time. And it is the only possibility that exists to take Lautaro away from Inter today."
Lautaro has been a major part of Inter's success this season, scoring 16 total goals as the Nerazzurri currently sit third in the Serie A table.
According to Ausilio, Inter's future success depends on keeping players like Lautaro rather than letting them go.
"He is an important asset of the club, and let's not forget that he still has a three-year contract with Inter," Ausilio said.
"Inter are not going to sell their most important players. We intend to keep them and eventually strengthen in the transfer market, and this also applies to Lautaro."
While Lautaro's future has dominated headlines, Brescia sensation Sandro Tonali has emerged as a target for Antonio Conte's Inter.
"Right now here maybe we have to see how [Christian] Eriksen is doing, but otherwise he is a great midfielder," Moratti said. "Then you will need someone on the wings, certainly."