Norberto Robles, federal prisoner # 82724-179, appeals the district court’s dismissal of his 28 U.S.C. § 2241 petition. The district court determined that Robles’ § 2241 petition was premature because his claims were directed to his criminal proceeding, which was active. We note that the district court appears to have treated Robles’ pleading as arising under § 2241, not § 2255. See Castro v. United States, 540 U.S. 375, 383, 124 S.Ct. 786, 157 L.Ed.2d 778 (2003). Robles’ brief is entirely devoted to the merits of his claims for relief. Although he asserts that he properly sought habeas relief pursuant to § 2241 because he filed his petition prior *945 to being sentenced, Robles provides no explanation for his conclusory assertion. By failing to address the basis for the district court’s dismissal, Robles has abandoned the threshold issue in this appeal. Yohey v. Collins, 985 F.2d 222, 224-25 (5th Cir. 1993); Brinkmann v. Dallas County Deputy Sheriff Abner, 813 F.2d 744, 748 (5th Cir. 1987).

AFFIRMED.