RIYADH, Saudi Arabia — Defense Secretary Chuck Hagel warned Pakistani leaders Monday that if they don’t resolve protests stalling some military shipments across the border with Afghanistan, it could be difficult to maintain political support in Washington for an aid program that has sent billions of dollars to Islamabad, defense officials said.

In response, the officials said, Hagel received assurances from the Pakistanis that they would take “immediate action” to resolve the shipment problem. The officials did not provide details on how that might be done.