Johnny Bernard Vaughn, a federal prisoner (#25787-177), appeals the district court’s sua sponte denial of his motion for reduction of sentence based on substantial assistance, purportedly filed pursuant to Fed.R.Crim.P. 35(b).

Only the Government can file a motion for reduction of a defendant’s sentence pursuant to Rule 35(b). United States v. Early, 27 F.3d 140, 141 (5th Cir. 1994) (citing Rule 35(b), historical note, 1991 amendment). Vaughn’s Rule 35(b) motion was “an unauthorized motion which the district court was without jurisdiction to entertain.” Id. at 142. Vaughn failed to make a “substantial threshold showing” of “unconstitutional motive” that might have permitted the district court to review the Government’s refusal to file a Rule 35(b) motion. See United States v. Wade, 504 U.S. 181, 185-86, 112 S.Ct. 1840, 118 L.Ed.2d 524 (1992).

The judgment of the district court is AFFIRMED.