A united U.N. Security Council strongly condemned North Korea's nuclear test and pledged further action Tuesday, calling Pyongyang's latest defiant act “a clear threat to international peace and security.’‘

All 15 council members, including North Korea's closest ally China, approved the press statement hours after the latest underground test. The statement called the atomic blast a “grave violation’‘ of three U.N. resolutions that ban North Korea from conducting nuclear or missile tests.

The swift and unanimous response from the U.N.'s most powerful body set the stage for a fourth round of sanctions against Pyongyang.

The language in the statement, which pledged “significant action’‘ in a new resolution, was stronger than the Security Council's initial reaction to North Korea's two previous nuclear tests and its most recent rocket launch. Diplomats said it reflects the growing anger at Pyongyang's continuing defiance of the council and the sanctions resolutions.

How tough the new sanctions will be will depend largely on China, North Korea's main trading partner. China has voted for the three previous sanctions resolutions but has resisted measures that would cut off the country's economy completely.

U.S. Ambassador Susan Rice said a number of new measures to tighten and expand the existing sanctions regime will be discussed with council members and other concerned countries in the coming days. She added in response to a question that financial sanctions would be “right for appropriate further action.’‘

Tuesday's nuclear test followed a familiar North Korean pattern. Pyongyang conducted its first two nuclear weapons tests weeks after rocket launches in 2006 and 2009, and this third test followed a rocket launch in December that the U.N. and the U.S. called a cover for a banned long-range missile test.

The Security Council noted that last month, in a resolution that strengthened sanctions in response to the December missile test, its members promised to take “significant action’‘ in the event of a new nuclear test.

“In line with this commitment and the gravity of this violation, the members of the Security Council will begin work immediately on appropriate measures in a Security Council resolution,’‘ the council said.

The statement was read by South Korea Foreign Minister Kim Sung-hwan, whose country holds the rotating Security Council presidency this month. South Korea was elected to the council for a two-year term starting in January.

“North Korea will be held responsible for any consequences of this provocative act,’‘ Kim told reporters later.

Rice called the test “highly provocative’‘ and said the North's continued work on its nuclear and missile programs threatens regional and international peace and “the security of a number of countries including the United States.’‘

“They will not be tolerated,’‘ she said, “and they will be met with North Korea's increasing isolation and pressure under United Nations sanctions.’‘

“The U.N. Security Council must and will deliver a swift, credible and strong response by way of a Security Council resolution that further impedes the growth of DPRK's nuclear weapons and ballistic missile programs and its ability to engage in proliferation activity,’‘ Rice said, using the initials of the North's official name, the Democratic People's Republic of Korea.

U.N. Secretary-General Ban Ki-moon welcomed the council statement and said he was encouraged by “the swift and overwhelming international condemnation of this wanton act.’‘

Ban, a former South Korean foreign minister, expressed regret that his repeated appeals to North Korea's new young leader, Kim Jong Un, to give up its pursuit of nuclear weapons and address international concerns through dialogue “have fallen on deaf ears.’‘

North Korea is the only country to carry out nuclear tests in the 21st century, he said, and the latest test in defiance of the U.N. and the international community “is a serious challenge to global efforts to curb nuclear proliferation.’‘

Ban said he is also “profoundly concerned about the negative impact of this act on regional stability.’‘ (AP)