A Chinese state-run newspaper blamed Washington Monday for the North Korean nuclear crisis and another stressed Beijing's limited scope for action, six days after tensions rose with a third atomic test.

The finger-pointing came as China's foreign ministry restated its "firm opposition" to the blast but mentioned no reprisals -- a mild reply compared to the condemnation and threats of tough sanctions by the US and other nations.

Beijing has propped up Pyongyang since the 1950-53 Korean War, for fear of instability that might bring refugees into its territory, a US-led military escalation in the region or even a unified Korea with a US military presence next door.

While Washington has pressed Beijing to use its trade and aid leverage over its dependent neighbour, some in China claim the US in fact holds greater sway as it can offer North Korea its most-sought-after prize of a security guarantee.

"The United States should take the major share of blame for rising tensions on the peninsula," the China Daily said, citing a researcher from the state-affiliated Chinese Academy of Social Sciences.

"The US did not respect the security concerns of (North Korea) and that is the reason why the nuclear issue on the Korean peninsula has not been solved," it said, paraphrasing an expert from the respected Tsinghua University.

Citing the same expert, the China Daily -- which put its story on the front page under the headline "US 'must act to ease peninsula tension'" -- accused Washington of using North Korea's nuclear pursuits as an excuse to build its regional military presence.

"Washington may not want Pyongyang's nuclear issue to be solved, because it offers an excuse for the US to deploy anti-missile systems and hold military drills in the region, which are in line with its military rebalance to East Asia," it said.

Meanwhile a Global Times editorial stressed the dilemma China faced in taking punitive steps against North Korea, which it said might both be futile and turn Pyongyang against Beijing in a split that would serve the US.

"Since Pyongyang's nuclear test has damaged China's interests, it's necessary for China to give Pyongyang a certain 'punishment'. The key problem is what the extent of this punishment should be," it said, adding: "Beijing is not an ally of Pyongyang."

"If Beijing takes a sharp turn in its attitude toward Pyongyang, it will become North Korea's top enemy, which is the desire of the US, Japan and South Korea," it said. "China must avoid this situation."