James Daniels pleaded guilty to disobeying court orders, in violation of 18 U.S.C. § 401(3), and the district court 1 sentenced him to 18 months imprisonment and 3 years supervised release. On appeal, counsel has moved to withdraw under Anders v. California, 386 U.S. 738, 87 S.Ct. 1396, 18 L.Ed.2d 493 (1967), and filed a brief raising the issue whether Daniels received effective assistance of counsel. Daniels filed a pro se motion to strike the Anders brief, as well as a supplemental brief arguing that the district court erred in giving him a 3-level increase for interference with the administration of justice.

We deny the motion to strike, and conclude that any ineffective-assistance claim should be raised in 28 U.S.C. § 2255 proceedings. See United States v. Jones, 121 *245 F.3d 369, 370 (8th Cir. 1997). We further conclude that the district court did not plainly err in giving Daniels a substantial-interference adjustment. See United States v. Evans, 272 F.3d 1069, 1089 (8th Cir. 2001); United States v. Plumley, 207 F.3d 1086, 1092-93 (8th Cir. 2000). Moreover, following our independent review, see Penson v. Ohio, 488 U.S. 75, 109 S.Ct. 346, 102 L.Ed.2d 300 (1988), we find no nonfrivolous issues.

Accordingly, we grant counsel’s motion to withdraw, and we affirm.