Speaking on ABC’s “This Week,” Mrs. Clinton said the United States feared that if the test and other recent actions by North Korea did not lead to “strong action,” there was a risk of “an arms race in Northeast Asia”  an oblique reference to the concern that Japan would reverse its long-held ban against developing nuclear weapons.

So far it is not clear how far the Chinese are willing to go to aid the United States in stopping North Korea’s profitable trade in arms, the isolated country’s most profitable export. But the American focus on interdiction demonstrates a new and potentially far tougher approach to North Korea than both President Clinton and Mr. Bush, in his second term, took as they tried unsuccessfully to reach deals that would ultimately lead North Korea to dismantle its nuclear arsenal.

Mr. Obama, aides say, has decided that he will not offer North Korea new incentives to dismantle the nuclear complex at Yongbyon that the North previously promised to abandon.

“I’m tired of buying the same horse twice,” Secretary of Defense Robert M. Gates said last week while touring an antimissile site in Alaska that the Bush administration built to demonstrate its preparedness to destroy North Korean missiles headed toward the United States. (So far, the North Koreans have not successfully tested a missile of sufficient range to reach the United States, though there is evidence that they may be preparing for another test of their long-range Taepodong-2 missile.)

In France on Saturday, Mr. Obama referred to the same string of broken deals, telling reporters, “I don’t think there should be an assumption that we will simply continue down a path in which North Korea is constantly destabilizing the region and we just react in the same ways.” He added, “We are not intending to continue a policy of rewarding provocation.”