The standoff between Italy and the J. Paul Getty Museum is intensifying, after the Italian culture minister threatened to cut off all cultural and scientific exchange with the museum if a deal is not struck in the next few weeks to resolve a dispute over 46 antiquities that Italy claims are looted.

Francesco Rutelli said yesterday that he sent the Los Angeles museum a final proposal to settle the matter. But if an agreement is not reached, a “real conflict will begin, a real embargo, that is the interruption of cultural and scientific collaboration between Italy and that museum,” he told the Associated Press.

A spokesman for the Getty, John Giurini, said that over the past few weeks, “There has been an exchange of letters between us and Rutelli, and we certainly hope it will lead to an agreement.”

He declined to elaborate on the nature of Italy’s proposal or whether it was acceptable to the Getty.

The Getty offered to return 26 objects to Italy last year, but the country is demanding an additional 21.

Negotiations broke down in November after the Getty refused to negotiate on one object the Italians are seeking, a fourth-century B.C.E. bronze statue of a youth.

Several sources contacted by The New York Sun said they did not know of another situation in which a country had threatened to discontinue all exchange with an American museum.

“This kind of threat, if true, is unprecedented and would raise the stakes immeasurably in the area of return of cultural patrimony,” an attorney who specializes in art law, Thomas Danziger, said.

Mr. Giurini said that while Italy sometimes loans objects to the Getty for exhibitions, the majority of the exchange goes in the other direction. The Getty Foundation makes grants to organizations and individuals in Italy; the Getty Conservation Institute works with Italian colleagues on conservation projects; and the Getty Research Institute funds Italian scholars to come to Los Angeles to conduct research.

“With the exception of loans … it’s unilateral support that we offer,” Mr. Giurini said. Asked whether Italians might decline to accept such support if an agreement on antiquities is not reached, he said: “It would be wrong for us to speculate at this stage on what an ‘embargo’ would mean.”

Other major museums have reached agreements with Italy over disputed antiquities. The Metropolitan Museum of Art last year made a deal to return several objects, includingthe Met’s prized Euphronios krater, in exchange for long-term loans of similar pieces. The Museum of Fine Arts in Boston cut a similar deal.

The former curator of antiquities at the Getty, Marion True, is currently on trial in Rome on charges of antiquities trafficking, along with the dealer Robert Hecht. Ms. True resigned from the Getty in 2005, after the museum determined that she had failed to report that she accepted a real estate loan arranged by a prominent antiquities dealer, Robin Symes, and his partner, Christo Michaelides.

Although it has failed thus far to reach an agreement with Italy, the Getty has taken steps to protect itself against future disputes.

It has adopted a policy of not acquiring an object unless documentation exists of its having been in America before 1970, its having been out of its original country before 1970 and legally imported into America, or its having been legally exported from its original country and legally imported into America after 1970.

In its quest for the return of what it considers its cultural patrimony, Italy has targeted private collectors, as well — most prominently a major patron of the Met, Shelby White.

Italy has asked Ms. White to return nine objects that it claims were looted. In May, the New York Times reported that negotiations were stalled over Ms. White’s demand that, in exchange for the return of the objects, she never be pursued by Italy again.