Biden's Mexico City agenda includes discussion of supply chains, fentanyl, climate change, immigration and drug cartels, Kirby said.

Asked about specific steps the United States would like to see Mexico take to stop the production and smuggling of fentanyl, Kirby said he didn't want to get ahead of the summit. "They're going to talk about a lot of this," he said.

The recent arrest of cartel leader Ovidio Guzman "is not an insignificant accomplishment by Mexican authorities," Kirby said. "It's not like we haven't had some success. I mean 20,000 pounds is a lot," he said, referring to the amount of the drug U.S. customs authorities have seized since last August.

"But it just keeps coming," Kirby said.

(Reporting by Jeff Mason; Writing by Heather Timmons; editing by Chris Reese and Diane Craft)