© 2016, The New York Times News Service

China has rejected criticism from the United States that its policies toward North Korea had failed, suggesting Friday that it was the Americans, not the Chinese, who were largely to blame for the North's embrace of nuclear weapons.In a stern rebuke that reinforced tensions between the world's leading powers days after North Korea claimed to have tested a hydrogen bomb, a Chinese official said that it was the responsibility of all countries - not just China - to persuade the North Korean government to abandon its nuclear program."The origin and crux of the nuclear issue on the Korean Peninsula has never been China," Hua Chunying, a spokeswoman for the Chinese Foreign Affairs Ministry, said at a regularly scheduled news conference in Beijing. "The key to solving the problem is not China."Hua did not mention the United States by name, but her remarks were a clear reference to the belief in China that efforts by the Americans to isolate North Korea economically and politically over the past decade have worsened the situation.U.S. officials have said that China, North Korea's main ally, is uniquely positioned to discourage the North's nuclear ambitions by cutting off oil shipments or disrupting its financial transactions. China is North Korea's biggest trading partner, and the two countries have been allies for six decades.On Thursday, Secretary of State John Kerry intensified pressure on Chinese leaders, saying that Beijing's attempts to rein in North Korea had failed. "We cannot continue business as usual," Kerry said at a news briefing in Washington.The United States is drafting a U.N. Security Council resolution to further disrupt trade in North Korea, including a partial ban on allowing North Korean ships to enter ports around the world, U.S. officials have said.Over the years, China has taken modest steps to limit North Korea's nuclear program, including banning weapons shipments. But it has stopped short of more crippling sanctions, in part because of a fear that destabilizing North Korea could send a wave of refugees into China and cede territory along its border to South Korea, a U.S. ally.China's president, Xi Jinping, who came to power in 2012, initially sought to keep a distance from the North, worried that its nuclear ambitions were threatening peace in the region. But in recent months, Xi sought warmer relations, sending a top official to meet with Kim Jong Un, the North Korean leader, in the fall.On Thursday, Kerry took aim at China's efforts to curry favor with the North. "China had a particular approach that it wanted to make, and we agreed and respected to give them space to be able to implement that," he said. "That has not worked."Since North Korea's claim of carrying out a nuclear test Wednesday - which experts doubt was of a hydrogen bomb, a far more powerful weapon than the low-grade atomic devices Pyongyang has detonated before - several public officials and news media commentators in China have denounced Kim. But many have defended the Chinese approach to dealing with North Korea, blaming other countries for escalating tensions in the region.A commentary Thursday in People's Daily, the Communist Party's flagship newspaper, said the United States had "inescapable responsibilities for the current tension in the peninsula."On Friday, Global Times, a nationalistic, state-run newspaper, issued a fiery rebuttal to Donald Trump, the Republican presidential candidate, who suggested that China should take the lead in stopping the North's nuclear program or face trade sanctions of its own."In no way will China bear the responsibilities that the U.S., South Korea and Japan should take," an editorial in the newspaper said. "The hostilities between them and Pyongyang are actually the source of the nuclear problems. The China-North Korea relationship should not be dragged into antagonism."