Michael Cohen made the request earlier this month, saying he should be released early as a reward for providing authorities information about alleged misdeeds by Trump.
But prosecutors in Manhattan say Cohen has offered no evidence that he provided substantial assistance to them. And they say Cohen's testimony before Congress should not win a reduction either.
Cohen claimed in filings in federal court in Manhattan that his continuing cooperation has included spending 10 hours with representatives from the office of Manhattan District Attorney Cyrus Vance Jr. during three meetings at a minimum security prison northwest of New York City.
The 53-year-old Cohen turned on the president last year by meeting with federal prosecutors in New York and with the office of special counsel Robert Mueller, telling them he had lied to Congress to protect Trump.
Cohen began serving his sentence last May after pleading guilty to lying to Congress, fraud and tax evasion charges. He is asking that his sentence be reduced to one year and one day or that he be allowed to serve the remainder under house arrest.