The government can seize a skyscraper in Midtown Manhattan that it says is controlled by Iran, a jury concluded on Thursday, allowing federal prosecutors to complete what they called the largest terrorism-related civil forfeiture in United States history.

The jury, which deliberated for one day after a month of testimony, found that the Alavi Foundation, which owns 60 percent of the 36-floor skyscraper at 650 Fifth Avenue, violated United States sanctions against Iran and engaged in money laundering through its partnership with Assa Corporation, a shell company for an Iranian state-controlled bank that had owned the remaining 40 percent.

Defense lawyers had argued that Alavi did not know of Assa’s ties to the Iranian government after the United States imposed sanctions in 1995.

The government has agreed to distribute proceeds from the building’s sale, which could bring as much as $1 billion, to the families of victims of terrorism, including the Sept. 11 attacks, where Iran has been found to have had some culpability. The office tower is highly coveted real estate; Nike recently signed a 15-year deal to rent seven of its 36 floors.