Sen. John McCain (R-Ariz.) said on Friday that "possible progress" was made in yesterday's nuclear negotiations with Iran in Geneva.

In Thursday's negotiations with permanent members of the U.N. Security Council, Iran agreed to ship low-enriched uranium overseas for further enrichment for peaceful purposes.

McCain, who is the top Republican on the Senate Armed Services Committee, however warned that the negotiators must later verify that Iran acted on their concessions.

He tweeted:

Possible progress with Iran on nukes. "Trust but verify" - Ronald Reagan.

Representatives from the United States, Britain, France, Russia, China, and Germany sat down with Iranian officials.

Russia and France would enrich the uranium for the Iranians under the agreement.