Secretary of State Marco Rubio pressed Lebanese President Joseph Aoun not to return a truckload of explosives to Hezbollah after the group tried to smuggle them into Beirut last week, according to a State Department official and another source with knowledge of their call.

Why it matters: The issue is a test case for the Lebanese government's resolve to stand up to Hezbollah and implement its policy of keeping weapons outside the control of state security forces.

Driving the news: Lebanese security forces intercepted the truck last week at a checkpoint on the highway connecting the Bekaa Valley to Beirut.

The truck was carrying approximately 780 kilograms of explosives, including TNT and C-4, Lebanese officials said.

Two suspects were arrested for transporting the shipment.

After the arrest, Hezbollah acknowledged that the explosives belonged to it but claimed they were intended for use against the Israeli military in southern Lebanon.

Hezbollah's opponents in Lebanon seized on the incident as further…