NEW YORK - The world's five leading nuclear powers -- all permanent members of the United Nations Security Council -- have issued a pledge to stop the spread of atomic weapons and to do all they can to ensure a nuclear war never occurs.

In a rare joint statement issued on January 3, France, the United States, Russia, China, and the United Kingdom said they were determined to prevent nuclear war and avoid a nuclear arms race.

"We affirm that a nuclear war cannot be won and must never be waged," the statement said.

"In view of the far-reaching consequences of the use of nuclear weapons, we also affirm that they, as long as they exist, must be used for defensive purposes, deterrence and prevention of war. We firmly believe in the need to prevent the further spread of these weapons," it added.

The statement was issued after the latest review of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) was postponed from January 4 to later in the year due to the COVID-19 pandemic.

The NPT, which took force in 1970, allows for signatories to gather every five years to review the treaty's operation. The conference was originally set for April 2020, but delayed due to the coronavirus pandemic.

In the January 3 joint statement, the five Security Council members reaffirmed the importance of dealing with nuclear threats and stressed the need "to preserve and respect our bilateral and multilateral agreements and commitments on non-proliferation, disarmament and arms control."

"We remain committed to fulfilling our obligations under the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), including that contained in Article VI to 'continue in good faith negotiations on effective measures relating to the cessation of nuclear weapons. early nuclear arms race and nuclear disarmament, and on a general and complete disarmament treaty under strict and effective international control.'"

The statement comes amid a rise in to near Cold War levels over a buildup of troops by Moscow close to the Ukrainian border, and tensions between the U.S. and China over human rights issues, a crackdown on pro-democracy groups in Hong Kong, and the situation around Taiwan.

Beijing said the statement will "increase mutual trust" among world powers, while officials in Russia said they hoped the pledge would help to reduce world tensions over global security.

Kremlin spokesman Dmitry Peskov told the RIA Novosti news agency that even with the pledge, Moscow still considers it "necessary" to hold a summit between the world's major nuclear powers to address outstanding issues.

"We hope that, in the current difficult conditions of international security, the approval of such a political statement will help reduce the level of international tensions," the Russian Foreign Ministry said in a statement.

The troop buildup has raised fears that the Kremlin is planning a new attack on its pro-Western neighbor. Meanwhile, the rise of China under President Xi Jinping has also raised concerns that tensions with Washington could lead to conflict, notably over Taiwan.

U.S. President Joe Biden and his Russian counterpart, Vladimir Putin, on December 30 held a phone call in which Biden said the United States and its allies would impose severe sanctions on Russia if it invades Ukraine.

During the call Biden warned Putin against invading Ukraine, while the Kremlin leader said anti-Moscow sanctions would be a "colossal mistake." But both leaders indicated support for further diplomacy, and talks between Russia and the U.S. on European security are expected to be held in Geneva early next week followed by other high-level meetings later in the month.

The NPT recognizes China, France, Russia, the U.K., and United States as nuclear weapons powers. India and Pakistan have also developed nuclear weapons, while Israel is widely believed to possess nuclear arms but has never officially acknowledged it has. India, Pakistan, and Israel are not signatories of the NPT. North Korea, which has also developed nuclear weapons, pulled out of the NPT in 2003.