A senior U.S. diplomat has called for the ratification of the Comprehensive Nuclear Test Ban Treaty, saying a legally binding total ban on nuclear explosive testing is necessary to bring to account countries like North Korea that insist on testing.

Rose Gottemoeller, under secretary of state for arms control and international security, made the remark in a speech in Alaska last week, stressing that it is in the interests of the United States to ratify the 1996 treaty, according to a transcript of her speech.

"In this century, only one country on Earth -- North Korea -- has conducted nuclear explosive testing. It is clear that a moratorium is not enough. We need a legally binding total ban on nuclear explosive testing to bring to account countries who insist on testing," she said.

North Korea conducted three nuclear tests, first in 2006 and then in 2009 and 2012.

Declaring its bomb-making nuclear facilities at the Yongbyon complex have returned to normal operations, the North hinted at the possibility of conducting its fourth nuclear test, saying it is ready to respond to U.S. "hostile policy" toward it with "nuclear thunder," a term apparently referring to a nuclear test.

Last week, South Korea's main intelligence agency reported to lawmakers that the North is preparing for the fourth nuclear test, though the chief U.S. nuclear envoy, Ambassador Sung Kim, said later that he has seen "nothing to indicate that a test is being planned."

Gottemoeller said that the CTBT was opened for signature in September 1996 and then-President Bill Clinton was the first world leader to sign the treaty, though the United States has yet to ratify it. Currently, 183 nations have signed the treaty and 164 have ratified it, she said.

The Senate refused to give its consent to ratification at the time as senators were concerned about mainly two issues: the ability to maintain the nuclear stockpile without explosive testing and the ability to verify compliance with the treaty, Gottemoeller said.

"Today the situation is entirely different," she said, citing advances in science and technologies.

She said the Stockpile Stewardship Program ensures that nuclear explosive tests are no longer necessary in order to ensure the safety, security and effectiveness of the nuclear weapons in the stockpile.

In addition, the International Monitoring System, the heart of the verification regime, was just a concept two decades ago, but it is nearly complete today and can detect even relatively low-yield nuclear explosions, she said.

U.S. President Barack Obama also called for the CTBT's ratification in his landmark 2009 speech in Prague, in which he called for a world without nuclear weapons, she said.

"U.S. ratification will help enhance our leadership role in arms control and nonproliferation and strengthen our hand in pursuing tough actions against suspected proliferators," Gottemoeller said. "It is in our interest to close the door on nuclear explosive testing forever." (Yonhap)