Arturo Ruiz-Ahumada pleaded guilty to illegal reentry following deportation, in violation of 8 U.S.C. § 1326(a) and (b), and the district court 1 sentenced him at the top of the Guidelines range to 87 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 has filed a brief in which he argues that the district court abused its discretion in sentencing Ruiz-Ahumada at the top of the Guidelines range. In a pro se supplemental brief, Ruiz-Ahumada raises speedy-trial, due process, and ineffective-assistance issues, all in relation to continuances the district court granted before he entered his guilty plea.

Counsel’s argument fails, as this court does not review a sentence merely because it has been imposed at the top of a Guidelines range that the defendant does not challenge. See United States v. Woodrum, 959 F.2d 100, 101 (8th Cir. 1992) (per cu *752 riam). Further, Ruiz-Ahumada’s guilty plea forecloses the speedy-trial and due process claims he raises in his pro se brief, see United States v. Beck, 250 F.3d 1163, 1166 (8th Cir. 2001) (valid guilty plea waives all nonjurisdictional defects); Cox v. Lockhart, 970 F.2d 448, 453 (8th Cir. 1992) (speedy-trial claim is nonjurisdictional and therefore waived by guilty plea), and his ineffective-assistance claim is not properly before us, see United States v. Martin, 59 F.3d 767, 771 (8th Cir. 1995).

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 affirm. We also grant counsel’s motion to withdraw.