United States Secretary of State John Kerry on Saturday said Pakistani scientist A.Q. Khan’s network, rather than China, was likely behind North Korea’s nuclear programme, even as he reiterated his call for the North to “refrain from provocations” amid continuing speculation about a missile launch and nuclear test being conducted in coming days.

Following talks with the Chinese leadership here on Saturday, Mr. Kerry said China had voiced its backing to the core goal of the stalled Six Party Talks mechanism which was “verifiable denuclearisation” of the Korean Peninsula.

Mr. Kerry did, however, refrain from going into specifics when asked if China had committed to any concrete steps in pressuring its ally to help tone regional tensions, with the North in recent days withdrawing from an armistice agreement and threatening strikes against U.S. bases in the Pacific in retaliation for military drills. Recent reports from Seoul have suggested the North is preparing to conduct a missile launch. Mr. Kerry only said both sides were intensifying engagement on the issue, with senior U.S. officials, including the chairman of the joint chiefs of staff, set to travel to Beijing in coming days.

In an interaction with reporters, the Secretary of State said he believed China had fully committed itself towards denuclearisation on the Korean Peninsula, when asked about whom he thought had aided the North’s controversial nuclear programme.

“I do not want to get into classified information here but I will tell you it doesn’t have to be, nor is there an insinuation, that it is China,” he said.

“There are plenty of places in world where non-proliferation has taken place over the years. Obviously, there is the A.Q. Khan network of Pakistan,” he said, adding that there were “lots of outside forces and that is one of the principal concerns of non-proliferation efforts around the world.”

“Yes I do believe what China’s intentions are here,” Mr. Kerry added. “There is no question in my mind that China is very serious about denuclearisation”.

U.S. officials did not say whether the recent agreement between China and Pakistan for a 1 GW nuclear reactor was brought up during talks on Saturday. It is, however, understood that the on-going civilian nuclear cooperation between the two countries has taken a back seat as the U.S. looks to secure Chinese support on the North Korean issue and on Iran.

Mr. Kerry said China and the U.S. had a “shared interest in preventing Iran from securing a nuclear weapon”, saying the issue was linked to the situation in North Korea.

Earlier on Saturday, Mr. Kerry met Chinese President Xi Jinping, who called on both countries to “interact positively in the Asia-Pacific region” and “step up communication and coordination on regional and international issues”, without directly mentioning North Korea.

The official Xinhua news agency in a commentary on Saturday issued to coincide with Mr. Kerry’s visit struck a less diplomatic tone. It hit out at the U.S. for “sending more fighters, bombers and missile-defence ships to the waters of East Asia and carrying out massive military drills with Asian allies in a dramatic display of preemptive power” while at the same time “accusing Pyongyang of reckless provocation”.