The Mexican government sent nearly 30 significant cartel operatives to the U.S., where American authorities have been seeking to charge them in federal courts.

Among those flown to the U.S. today was Rafael Caro Quintero, a founding member of the Sinaloa drug cartel who was convicted in Mexico of having masterminded the 1985 murder of the D.E.A. agent Enrique Camarena. For decades, American officials have obsessed over getting hold of him.

The transfer came as a high-level delegation from Mexico arrived in Washington to meet with senior U.S. officials on a security agreement at a moment of tension between the nations. It was hailed in American law enforcement circles as a major victory and a clear signal that Mexico’s president planned to cooperate with the Trump administration in cracking down on the cartels.

Inside the White House, there are also tensions. Some U.S. officials have pushed for unilateral military action against the cartels. Others have argued for increased partnership with the Mexican government, in part to ensure cooperation on migration.