Quotes of the Day

North Korea, defying urgent pleas and intense pressure from the rest of the world, successfully tested a nuclear bomb this morning at a site near the city of Kilju in country's northeast, about 400km from the capital Pyongyang. The test moves the issue of Pyongyang's nuclear capability into a tense new phase. For more than a decade, the United States and North Korea's neighbors in east Asia—South Korea, Japan China and Russia—have worked to get Pyongyang to abandon its nuclear ambitions. Those efforts have proved fruitless, and indeed the timing of the North's test today seemed particularly pointed. On Sunday, Shinzo Abe, Japan's new prime minister, visited Beijing, where he and Chinese premier Hu Jintao insisted that the North must not be allowed to test a nuclear bomb. Abe is in Seoul today for talks with President Roh Moo Hyun.

Pyongyang's ability to "weaponize" its nuclear materials—to place a bomb on a missile for delivery—is still uncertain. So is the capability of its longest-range missiles: this summer, in defiance of the international community, Pyongyang test fired an intercontinental ballistic missile that analysts said could reach Alaska or Hawaii. That test failed, but a test of a shorter range missile—one that could easily reach Japan—was successful.

What the U.S. and its partners in the so-called six party talks with Pyongyang will do now is not clear. The U.S., Japan, China , South Korea and Russia have struggled to present Pyongyang with a united front in efforts to get it to stand down on its nuclear program. Washington and Tokyo have called for—and in some cases, implemented—tough sanctions against Pyongyang for its refusal to negotiate. South Korea and China—on whom the North depends for critical oil supplies—have sought a less confrontational approach to Pyongyang, in part because both would bear the brunt of any potential economic collapse in North Korea.

But this summer it was evident that even Beijing's patience with North Korea's dear Leader, Kim Jong Il, was wearing thin. In late July, China agreed to freeze accounts at a Macau-based bank that Washington claims was being used by senior North Korean officials to launder tens of millions of dollars. In recent weeks, both South Korean and U.S. officials told TIME that they believed the sanctions were "really biting," as one US source put it, and had "infuriated" the North Korean regime. Many analysts speculated, in fact, that the North's test threats were in part a display of its anger over the sanctions.

The North's claim of a successful test now moves the issue squarely back into Washington's court. Pyongyang wants direct talks with the U.S., a removal of the sanctions and a range of security guarantees in return for backing off its nuclear program. In a tough speech last week, the U.S. State Department's point man on the North Korean nuclear issue, Ambassador Christopher Hill, said the U.S. could not live with a nuclear test. What precisely that means is something that Washington, in consultation with Beijing, Seoul and Tokyo, will now be trying to figure out. Few analysts believe a viable military option exists. The potential costs, including a likely North Korean retaliation against South Korea, are too huge to contemplate. Beijing, to be sure, did not want Pyongyang to test—and North Korea's defiance is a distinct loss of face for China, the one country thought to have some influence in North Korea. According to Kurt Campbell, director of the International Security Program at Washington's Center for International Security, the test could also force Japan and South Korea to potentially increase their defence spending and even push the U.S. to strengthen its security commitment to the area—neither of which China wants.

But the test may not alter China's basic calculus when it comes to Pyongyang: most analysts believe that, more than anything, Beijing wants stability on its long border with the North. Alexandre Mansourov, a North Korea expert at the Asia-Pacific Center for Security Studies in Hawaii, warns that China's response could be milder than expected: "They'll want slap symbolic sanctions, but I don't think the Chinese will vote for tough language or enforce any sanctions the U.N. Security Council decides to pass." If that's true, the ability of the outside world to register its displeasure with Pyongyang may be limited.

• Bill Powell
• With North Korea claiming a successful nuclear weapons test, its neighbors and the U.S. must figure out how to respond