BEIJING — After a day of meetings with senior Chinese officials, Secretary of State John Kerry asserted on Friday that China was prepared to step up the pressure on North Korea to abandon its nuclear weapons programs.

Mr. Kerry said he had urged President Xi Jinping and other senior Chinese officials to “use every tool at their disposal” to persuade North Korea to rethink its decision to be a nuclear power.

Chinese officials, Mr. Kerry added, had made it clear that they supported the denuclearization of the Korean Peninsula “over the long run” and were prepared to take “additional steps” if North Korea was not willing to stop its nuclear effort and begin serious negotiations.

But Mr. Kerry acknowledged that significant differences remained between the United States and China over the specifics of how to rein in North Korea’s nuclear programs. And some experts noted that a similar appeal that Mr. Kerry made in April for China to use its leverage with Pyongyang did not appear to have much effect on North Korea’s nuclear activities.