UNITED NATIONS: New nuclear sanctions against North Korea agreed by the UN Security Council on Thursday will "bite hard," the United States said but China called for new efforts to get the North back to talks.The United States and its allies angrily renewed condemnation of the North's February 12 nuclear test and its threat on Thursday to stage a "pre-emptive" nuclear strike. South Korea's UN envoy warned that the rival state could be on the path to "self-destruction"."Taken together, these sanctions will bite and bite hard," US ambassador Susan Rice told reporters after the vote."They increase North Korea's isolation and raise the cost to North Korea's leaders of defying the international community," she added.The sanctions step up financial restriction, add new names to a UN blacklist, tighten rules for inspections of North Korean cargo and specifically ban exports of luxury cars, yachts and jewelry to Pyonyang.The North has responded by declaring it will withdraw from an armistice that halted the 1950-53 Korean War and that it could launched "a pre-emptive nuclear attack.""North Korea will achieve nothing by continued threats and provocations. These will only further isolate the country and its people," said Rice.The United States and China negotiated the tougher sanctions, but China was not among nations which sponsored Resolution 2094.China has traditionally sought to shield its neighbor from tough international action.But China's UN envoy Li Baodong said "the resolution just adopted by the Security Council is a reflection of the view and determination of the international community against the nuclear program.""We want to see full implementation of the resolution," Li told reporters.But he added that "the top priority now is to defuse the tension, bring down the heat, focus on the diplomatic track."The resolution stressed the importance of six nation nuclear talks among the United States, Japan, South Korea, Russia, China and the North which have been moribund since 2009."We encourage all the stakeholders: talk with each other," said Li.South Korea is a current member of the Security Council and its envoy Kim Sook called the North's new threats "deplorable"."Each violation will be met by stronger responses and measures," Kim told reporters as he welcomed the resolution."North Korea must wake up from its delusion of becoming a nuclear weapons state and make the right choice," said Kim, declaring that his country's arch-rival was now at a "crossroads"."It can either choose the right path toward a bright future and prosperity, or it can take the bad road toward further and deeper isolation and eventual self-destruction," he said.Observers have expressed doubts that the sanctions will change North Korea's behaviour."The new sanctions are a clear sign that China's impatience with North Korea is growing, but they do not move us any closer to a real solution," said Suzanne DiMaggio, vice-president of the Asia Society, a US policy forum."What's needed is direct dialogue between Beijing, Washington, and Seoul with Pyongyang," she added."The ratcheting up of hostile rhetoric toward the US on Pyongyang's part should move the Chinese to work harder to defuse the situation. A more robust US military presence in Northeast Asia that serves to strengthen capabilities of American allies is the last thing Beijing wants right now," said DiMaggio.