Sarkozy said the airborne component would be cut by one-third, specifying that this included nuclear weapons, missiles and planes.
"After this reduction, our arsenal will include less than 300 nuclear warheads," he said on Friday.
"That is half the maximum number of warheads that we had during the Cold War."
Sarkozy made the announcement in Cherbourg, northwestern France, at the inauguration of the country's fourth nuclear-armed submarine, named the 'Terrible'.
Nuclear testing ban
In his first major speech on defence since becoming president, Sarkozy also urged China and the United States to ratify a treaty banning tests of nuclear weapons.
The Comprehensive Nuclear Test Ban Treaty was signed in 1996 and ratified by France a decade ago.
Sarkozy noted that while France does not face a foreseeable threat of invasion, other dangers exist.
He singled out Iran's development of its missile forces and the "grave suspicions" surrounding its nuclear program.
"The security of Europe is at stake," Sarkozy said adding that France needs to be able to strike back if attacked.
"Everyone must be aware today that even far-flung powers' nuclear missiles can reach Europe in less than half an hour."
The UN security council has passed three rounds of sanctions against Iran for failing to allay fears that it is trying to develop nuclear weapons under the cover of a civilian power programme.
Iran, which denies the charges, continues to expand its long-range missile programme.
Its claim that it can hit targets that are 2,000 km (1,250 miles) away has raised concern in the West.
Referring to the Islamic Republic, Sarkozy said: "In the face of proliferation, the international community must be united."
The president also warned that countries in Asia and the Middle East are conducting a "forced march" to acquire ballistic missile capabilities.
"The international community must be resolute. Because we want peace, we must be without weakness with those who violate international norms.
"All those who threaten to attack our vital interests would expose themselves to a severe riposte by France," he said.
Sarkozy also proposed measures to limit nuclear stockpiles.