Federal prosecutors in Manhattan asked a judge on Friday to impose a life sentence on Viktor Bout, a former Soviet military officer convicted in November in an arms trafficking and terrorism conspiracy, a court filing shows.

The United States attorney’s office made the request in a memorandum to Judge Shira A. Scheindlin of Federal District Court, who is to sentence Mr. Bout on Thursday.

Mr. Bout, 45, was convicted of conspiring to sell millions of dollars worth of weapons, including antiaircraft missiles, to men he believed were terrorists intending to kill Americans. One count carries a 25-year mandatory minimum sentence, but prosecutors said that would be insufficient, given that Mr. Bout had been ready to deliver 700 to 800 surface-to-air missiles as part of the proposed deal.

Mr. Bout was taken into custody in Thailand in March 2008 after becoming ensnared in an international sting operation run by the Drug Enforcement Administration. The sting used cooperating informants posing as representatives of a Colombia terrorist group, the Revolutionary Armed Forces of Colombia, or FARC. He was later sent to the United States for prosecution.