ROME — The food rations and medical supplies that Secretary of State John Kerry said Thursday would be provided to the Free Syrian Army mark the first time that the United States has publicly committed itself to sending nonlethal aid to the armed factions that are battling President Bashar al-Assad.

But the nature of the assistance also illustrates the Obama administration’s caution about getting involved in the Syrian crisis.

At each stop of his first foreign trip as secretary of state, Mr. Kerry has emphasized that one of his principal goals is to change Mr. Assad’s calculations about his ability to remain in power.

Mr. Assad is “out of time and must be out of power,” Mr. Kerry asserted after meeting here with Moaz al-Khatib, the leader of the Syrian opposition coalition.