United Nations Secretary General Ban Ki-moon on Friday urged the last countries that have not yet ratified the Comprehensive Nuclear Test Ban Treaty (CTBT) to let it enter into force.

Nine countries, notably the United States and China, are still preventing the 15-year-old treaty from taking effect. The treaty bans nuclear explosions for either military or civilian purposes.

"Do not wait for others to move first. Take the initiative. And lead. The time for waiting has passed," Ban said during a meeting in New York on the margins of the UN General Assembly.

"That is why I urge all remaining states to sign and ratify the CTBT without further delay," he told an audience of foreign ministers from countries that are party to the treaty.

Ban stressed his personal engagement in efforts to ratify the CTBT, noting that his name "Ban" reflected his desire to ban nuclear explosions.

"My name is spelled Ban, it is pronounced 'Bahn' but some people pronounce 'Ban.' Therefore my name has a very clear, firm determination," the UN chief declared.

The CTBT -- which is seen by arms control advocates as a key measure for preventing the spread of nuclear weapons -- has so far been signed by 182 countries and ratified by 154 of them.

But rules on ratification have meant the text, which was adopted by the UN General Assembly on September 10, 1996, is still far from being implemented, and could well never be.

The treaty will not take force until ratified by the United States, China, Egypt, Indonesia, Iran and Israel (which have signed but not ratified it) as well as North Korea, India and Pakistan (which have not signed it).

Full entry into force of the CTBT would be "a major step forward for global security," French Foreign Minister Alain Juppe said at Friday's meeting.

The unwillingness of the United States to ratify the treaty has been a key obstacle, with many analysts saying that US ratification would encourage other holdout countries to follow suit.

In April 2009, US President Barack Obama raised hopes when he said he would seek US Senate ratification of the CTBT, but Washington has since put the treaty on hold.

The CTBT also calls for a global system for monitoring nuclear explosions, which has been partially set up.

Of the 337 monitoring stations planned as part of the network, about 80 percent of them are ready.

The data recorded has helped authorities put out earthquake and tsunami warnings, such as after the March 11 disaster in Japan.

Advocates of the treaty argue that it also would help prevent harm from the radioactive fallout of atomic bomb tests.

"In five decades of nuclear testing we have seen more than 2,000 nuclear tests," German Foreign Minister Guido Westerwelle said.

"The level of radiation set free by these tests has been many times higher than that set free by the nuclear power plant accidents of Chernobyl and Fukushima."