PARIS -- President Nicolas Sarkozy said Friday that he will cut France's nuclear arsenal to fewer than 300 warheads, seeking to balance the defense of the nation -- he mentioned the threat from Iran -- against budgetary and strategic considerations.

In addition, Sarkozy shifted somewhat from the nuclear doctrine of his predecessor, Jacques Chirac, by being slightly more ambiguous about the circumstances that might lead France to employ its nuclear weapons.

Sarkozy's decision to reveal the rough size of France's arsenal -- the Defense Ministry said the exact number of warheads is still secret -- appeared aimed at prodding other nuclear powers to be equally transparent.

Many of France's nuclear weapons are carried aboard submarines, with the rest on warplanes. Sarkozy said the airborne component would be cut by one-third, specifying that that included nuclear weapons, missiles and planes.

"After this reduction, our arsenal will include fewer than 300 nuclear warheads," he said. "That is half the maximum number of warheads that we had during the Cold War."

He also said none of France's weapons is targeted at any nation.

France's airborne nuclear weapons are carried by three air force squadrons of Mirage 2000N and another navy flotilla of upgraded Super Etendard jets. They are all to be replaced by high-tech Rafale jets, in air force and navy versions.

French defense expert Francois Heisbourg said the air fleet modernization allowed the size of the nuclear arsenal to be trimmed.

"When you have better planes taking over for older planes, you can afford to reduce the numbers," said Heisbourg, special adviser to the Paris-based Foundation for Strategic Research think-tank.

"That doesn't make us virtuous guys in itself, although of course it's nicer to say the numbers are going down than the numbers are going up. What does make us more virtuous than we were before is by saying 'By the way, that means we're going to have 300.' And that meaning is, 'Oh by the way, dear Chinese friends, you better tell us how many you've got.' "

The Federation of American Scientists, which tracks nuclear arsenals around the globe, said in a status report for 2008 that France had 348 strategic nuclear weapons. It lists 193 for China and 160 for Britain, all far less than the United States, with 3,575, and Russia, with 3,239.

Since Sarkozy is France's first leader born after World War II, his reaffirmation of the need for nuclear weapons, despite France's budgetary difficulties, was significant. It marked a continuation of French policy despite a generational shift in political leadership.

He called the nuclear arsenal "the nation's life insurance."

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 -- which France and other Western powers fear is aimed at developing weapons.

"The security of Europe is at stake," Sarkozy said.

Donning his commander-in-chief cap also was part of a new effort by Sarkozy to appear more presidential. Following a divorce in office, then a quick marriage to former model and singer Carla Bruni, and outbursts of temper, Sarkozy has faced criticism for behavior perceived as unbecoming for a head of state.

Sarkozy gave his speech in the northern port of Cherbourg to personnel building a nuclear submarine, The Terrible, the fourth in a new generation of nuclear-powered and armed French subs. The Terrible will undergo tests in the Atlantic in 2009 and go into service a year after that, carrying new M51 nuclear missiles with multiple warheads and a longer range than current missiles.

Sarkozy used his announcement of French weapons cuts to drive home calls for other nations to dismantle nuclear test sites and for negotiations on treaties to ban short- and intermediate-range ground-to-ground missiles and to ban the manufacturing of fissile material for nuclear weapons. He also pressured to China and the United States to ratify a nuclear test ban treaty they signed in 1996. France ratified it a decade ago, and Russia is a signatory to the treaty.

State Department spokesman Sean McCormack said he had not seen Sarkozy's appeal.

"I haven't seen his comments, but the United States has not conducted a weapons test in a couple decades, as far as I know," McCormack said.

Heisbourg said ratification by China and the United States would "put pressure on countries that have been building things that look like test sites, like the North Koreans or, indeed, the Iranians."

He also said a global treaty banning intermediate-range missiles could put severe pressure on India, Iran, Pakistan and North Korea -- which all have either tested nuclear weapons or are thought to have programs to develop them -- to join the ban or "pay a political price."

• Associated Press writers Jenny Barchfield in Paris and Christine Ollivier and Angela Doland in Cherbourg, France, contributed to this report.