Ex-Soviet President Mikhail Gorbachev said the five original nuclear powers have not done enough to eliminate nuclear weapons and prevent other nations from acquiring them.
Consequently, India, Pakistan, Israel and most recently North Korea have joined the club, Gorbachev said Sunday at the screening of a CNN television series on the Cold War at the Museum of Television & Radio.
"This is not good that this is happening," Gorbachev said, speaking briefly to reporters through an interpreter.
The four countries he named are not among the nearly 190 that signed the 1970 Nuclear Non-Proliferation Treaty. In the past week, North Korea announced it had carried out an underground nuclear test blast.
Under the treaty, the five original powers the United States, Britain, France, Russia and China were allowed to keep nuclear weaponry.
If the five undermine the treaty, he said, more than 30 countries capable of producing the weapons will say that if the five "are preserving and modernizing their nuclear weapons, why should we be hostages to this situation?"'
"This is a very serious situation," he said.
When asked whether North Korea was trying to scare the world or the other way around, the 75-year-old former Kremlin leader replied, "I think both sides are trying to scare the other side."
Twenty years ago this month at a summit in Iceland, Gorbachev and President Ronald Reagan reached a surprise agreement on removing intermediate-range missiles from Europe and limiting nuclear warhead numbers elsewhere, reports AP.
The next year in Geneva, the two parties signed a formal nuclear weapons agreement that would be a key step toward ending the Cold War. He was awarded the Nobel Peace Prize in 1990.
Having left office when the Soviet Union collapsed in December 1991, Gorbachev now runs a foundation devoted to international issues, including globalization, security, weapons of mass destruction and poverty.