Can a federal district court dismiss a habeas petition without resolving whether all the claims have been exhausted?

We have interpreted Rule 4 to authorize a district court to "dismiss a habeas petition without resolving whether a petitioner has exhausted available state remedies when on the face of the petition it is obvious that the petition lacks merit." Gutierrez v. Griggs, 695 F.2d 1195, 1198 (9th Cir.1983). Requiring a district court to determine whether all the claims in a meritless petition have been exhausted "would be wasteful and inefficient" and "would place a correspondingly higher burden on state and federal judicial resources." Id.