China is North Korea's only real ally in the Asia Pacific, and critics say it has failed to fully enforce international sanctions levied against the smaller country -- even though it voted for many of them -- sustaining a government that could otherwise likely collapse.
"China had a particular approach that it wanted to make" in dealing with North Korea, Kerry told reporters at a press briefing Thursday, recalling his first trip to Beijing as secretary. "And we agreed and respected to give them space to be able to implement that."
However, he said Thursday that the approach was no longer welcomed by the United States.
"Today in my conversation with the Chinese I made it very clear: That has not worked and we cannot continue business as usual," he said.
The U.S. is asking China to not only support more robust action at the U.N., but to apply its own unilateral economic pressure, as North Korea's largest benefactor.
U.S. officials said the administration at all levels is stressing to China that it should be very concerned that North Korea did not warn China about the test ahead of time, thus illustrating the danger of the regime's unpredictability.
Kerry's unusually pointed comments toward China came amidst harsh criticism of the Obama administration for not taking a harder line against North Korea, which has now conducted three nuclear tests under its watch. It claimed the last, on Tuesday, was a hydrogen bomb, though the White House has shed doubt on that assertion.
Among the most strident have been Republican presidential candidates, including billionaire businessman Donald Trump, who called for the U.S. to push China to do more to reign in Pyongyang.
Donald Trump, the front-runner for the GOP nomination, told CNN's Wolf Blitzer on Wednesday that "China should solve that problem, and we should put pressure on China to solve the problem."
Florida Sen. Marco Rubio, another presidential candidate, said in a statement that the nuclear test, if confirmed, "will be just the latest example of the failed Obama-Clinton foreign policy," referring to Kerry's predecessor and the current Democratic front-runner, Hillary Clinton.
And former Florida Gov. Jeb Bush told reporters on the campaign trail that the nuclear test was "an example of a withdrawn America in the world."
Chinese officials are also shifting the blame to Obama, condemning North Korea's nuclear provocations and telling CNN they believe the U.S. could be exerting more influence on North Korean leader Kim Jong Un if it wanted to, since Kim has long sought direct communication with Washington.
Kerry, for his part, took issue with those contentions, emphatically maintaining that, "North Korea has never been left unattended to. Not for one day."