"It's a very important deal that was signed overnight, the world is making headway," he said in his traditional annual televised interview on France's national day.
"Now that Iran will have bigger financial capabilities -- as there will no longer be sanctions -- we must be extremely vigilant on what Iran will be," he added.
"Iran must show... that it is ready to help us on Syria to end this conflict."
Reached on day 18 of marathon talks in Vienna, the deal aims at resolving a 13-year standoff over Iran's nuclear tensions after repeated diplomatic failures and threats of military action.