Brazilian officials said they were hopeful that the authorities in the United States would get involved. After all, Chicago was one of the cities that Rio edged out in the competition to host the Games. The American city’s bid had been championed by President Barack Obama and Oprah Winfrey, both of whom traveled to Copenhagen on the eve of the announcement, hoping to sway committee members.

Yet, Brazilian prosecutors said they felt stonewalled by the Americans after they suggested that United States authorities freeze Mr. Soares’s bank accounts and execute a search warrant on his residence in coordination with the other raids on Sept. 5.

“It was frustrating,” said Vladimir Aras, a senior Brazilian prosecutor who until recently served as the head of international cooperation at the attorney general’s office in Brasília. “It would have been more fruitful for the collection of evidence if we had counted with the cooperation of the United States.”

Brazilian prosecutors say they fear that Mr. Soares may have shielded his assets, and potentially gone into hiding, in recent days. They consider him a flight risk because Mr. Soares had been seeking to obtain Uruguayan and Portuguese citizenship, possibly in an effort to dodge extradition.

The first official response that Brazil received from the United States government was delivered on Sept. 5 in a four-page diplomatic note submitted by the State Department.

The note said that Brazil’s request had failed to meet the evidentiary standard for extradition. It questioned the strength of some of the evidence that the Brazilians had submitted in the affidavit.

The Justice Department declined to comment on the specifics of the case.

“The United States is not a safe haven for fugitives from any nation,” Wyn Hornbuckle, a spokesman, said Wednesday. “We value our strong law enforcement relationship with Brazil. As a matter of policy, the department does not comment on specific extradition processes, but we are committed to working together on these matters.”