PER CURIAM:

Defendants-Appellants pled guilty in the Southern District of New York (Cathy Seibel, Judge) to conspiring to distribute a controlled substance in violation of 21 U.S.C. §§ 841(a), 841(b), and 846, and to using and carrying a firearm during and in relation to that conspiracy in violation of 18 U.S.C. § 924(c). The district court sentenced all three defendants to the mandatory minimum term of imprisonment on both counts, ten years for the drug charge,1 and five years for the gun charge. At issue in this sentencing appeal is whether the district court had authority to impose less than the mandatory minimum sentences by running those sentences concurrently to completed prison terms appellants previously served on related state charges.

Appellants all participated in the charged conspiracy for several years prior to their federal indictment. All served time in state prison for crimes that were part of the conspiracy and those offenses were "relevant conduct" under U.S.S.G. § 1B1.3 for the federal crimes. All finished serving those sentences before they pled guilty in federal court. But at sentencing, the district court concluded that it did not have authority to adjust appellants' sentences by running those sentences concurrently to those discharged terms.

The Sentencing Guidelines instruct district courts to run a prison term "concurrently to the remainder of [any] undis charged term of imprisonment" if the recommended "term of imprisonment resulted from another offense that is relevant conduct to the ... offense of conviction." U.S.S.G. § 5G1.3(b). In other words, when the defendant is serving time on a prior conviction that relates to the new charge, the Guidelines direct that the defendant serve the new sentence parallel to the old.2 The Sentencing Commission grounds the Guideline in the power vested in district courts by 18 U.S.C. § 3584(a). See § 5G1.3 cmt. background. That statute gives district courts discretion to run a sentence concurrently where "a term of imprisonment is imposed on a defendant who is already subject to an undischarged term of imprisonment," although the statute also makes clear that a court retains the discretion to run terms consecutively when it sees fit. In United States v. Rivers, 329 F.3d 119 (2d Cir.2003), we held that a 46-month sentence did not dip below the mandatory 60-month statutory minimum because it actually reflected a 64-month sentence imposed concurrently with an undischarged state term of imprisonment where the defendant had already served 18 months. The adjustment for the 18 months already served was "similar to that of a credit," and was "no less proscribed by the statutory minimum than where the prisoner is credited by the BOP for time already served." Id. at 122.

On appeal, as before the district court, appellants argue that the principle embodied in § 5G1.3(b) and applied in Rivers applies with equal force to prison terms that defendants have already served. In other words, appellants urge this court to stretch the meaning of "undischarged term of imprisonment" in § 5G1.3(b) to encompass discharged terms of imprisonment. Were we to interpret § 5G1.3(b) as appellants suggest, the district court would be authorized to sentence all three appellants to serve less time in federal prison than the mandatory 15-year terms imposed by the court.

We reject appellants' argument.3 Section 5G1.3(b) cannot be interpreted to mean more than it says. The text refers only to "undischarged" prison terms.4 Even if that word were ambiguous, which it manifestly is not, the Guideline would still be constrained by the limits of its enabling statute. As the First Circuit has explained, "[a] defendant's eligibility for [a benefit under § 5G.1.3(b)] is derivative of his eligibility for a concurrent sentence" under 18 U.S.C. § 3584. United States v. Ramirez, 252 F.3d 516, 519 (1st Cir.2001). And § 3584 delineates two categories of defendants who qualify for a concurrent sentence: those subject to "multiple terms of imprisonment ... imposed ... at the same time," and those who are "already subject to an undischarged term of imprisonment." Nothing in the statute authorizes the district court to extend the benefit of a concurrent sentence to a third category of defendants, those who have previously served sentences, now completed, for related crimes.

Our decision in Rivers offers appellants no comfort. As noted above, we held there that adjusting a sentence to run concurrently with an undischarged term of imprisonment is "no less proscribed by the statutory minimum than where the prisoner is credited by the BOP for time already served." 329 F.3d at 122. But as that passage from Rivers suggests, absent express statutory authority, a statutory minimum term of imprisonment does "proscribe" the conferral of a sentencing break.5 A district court must impose a mandated minimum unless a more specific statutory provision allows the court to impose a lower sentence. As we explained in United States v. Labeille-Soto, 163 F.3d 93 (2d Cir.1998), § 3584(a) does not provide courts with such a power in this case: "From th[e] section's use of the modifier `undischarged,' it may reasonably be inferred that Congress did not intend to allow the court to make a new prison term run concurrently with a prison term that has already been completed." Id. at 98.

Appellants suggest that 18 U.S.C. § 3553 endows courts with authority to craft a reasonable sentence that reflects time already served on related state charges. But we have held that the general instructions in § 3553 cannot trump a specific statutory command to impose a minimum sentence. See United States v. Samas, 561 F.3d 108, 110 (2d Cir.2009) ("[A] district court must impose a statutorily mandated sentence even if the court would reach a different determination if it considered only § 3553(a)"). Thus, the appellant in Rivers was in a different position than the appellants here—Rivers could point to a statute that authorized the court to adjust his sentence in light of his time in state prison, while appellants here cannot.6

Lucas (but not the other appellants) argues that our reading of U.S.S.G. § 5G1.3(b) and 18 U.S.C. § 3584 may lead to irrational results. A defendant who finishes serving a state term while awaiting a hearing date in federal court, for example, will not receive the benefit of a concurrent sentence even though he might have qualified for one had the federal case proceeded more quickly. Lucas argues that this renders the statutory distinction between undischarged and discharged sentences unconstitutional under the equal protection component of the Fifth Amendment's due process clause. But as Lucas concedes, the distinction between unfinished and completed sentences need only survive rational basis review to pass constitutional muster. See Griffin v. Mann, 156 F.3d 288, 291 (2d Cir.1998) (applying rational basis scrutiny to sentencing enhancements). Under that generous standard of review, the "differential" between sentences "must be upheld against an equal protection challenge if there is any reasonably conceivable state of facts that could provide a rational basis for the classification." United States v. Thomas, 628 F.3d 64, 70 (2d Cir.2010) (brackets omitted).

Therefore, in order to prevail on this claim, Lucas must overcome the "challenged classification['s] strong presumption of validity" by rebutting "every conceivable basis which might support it." Id. at 70-71 (internal quotation marks omitted). Lucas has not met this considerable burden. While Lucas has suggested that his individual circumstances do not present the same concerns that might have motivated Congress to distinguish between discharged and undischarged sentences,7 he fails to demonstrate that there are no plausible reasons for Congress to have drawn the distinction at issue. See FCC v. Beach Commc'ns, 508 U.S. 307, 313-14, 113 S.Ct. 2096, 124 L.Ed.2d 211 (1993).

In sum, we hold (1) that neither U.S.S.G. § 5G1.3 nor 18 U.S.C. § 3584 authorizes a district court to run a term of imprisonment concurrently with a discharged term of imprisonment on related charges, and (2) that those provisions' distinctions between discharged and undischarged terms are not irrational.

We have reviewed appellants' remaining arguments and conclude they are without merit. Accordingly, the judgment of the district court is hereby AFFIRMED.