China firmly opposes a United States report that portrays Beijing as a potential nuclear adversary and calls on Washington to honor its commitments to reduce its own nuclear arsenal, a Ministry of National Defense spokesman said on Sunday.

The report, titled the Nuclear Posture Review, was published by the US Defense Department on Friday. It cites China as "a major challenge to US interests in Asia".

The US strategy for China is designed to "prevent Beijing from mistakenly concluding that it could secure an advantage through the limited use of its theater nuclear capabilities or that any use of nuclear weapons, however limited, is acceptable", according to the document.

The report speculates on China's intention of development and plays up the threat of China's nuclear strength, said Ren Guoqiang, National Defense Ministry spokesman.

Ren reaffirmed China's policy of "no first use of nuclear weapons at any time under any circumstances".

"Under no circumstances will China use or threaten to use nuclear weapons against non-nuclear weapon states or nuclear-weapon-free zones," he said.

Ren said that China has always exercised the utmost restraint in the development of nuclear weapons and limited its nuclear capabilities to the minimum required for national security.

As the country that possesses the world's largest nuclear weapons arsenal, the US should conform to the irreversible world trend of peace and development rather than run in the opposite direction, Ren said.

"We hope the US will discard its Cold War mentality, shoulder its own special and primary responsibility in nuclear disarmament, correctly understand China's strategic intention and take a fair view on China's national defense and military development," he said.

The US report reaffirms commitments to nonproliferation treaties, but it emphasizes the need to enhance capabilities to match Russia, showing support for US nuclear modernization projects.

It calls for a "lower-yield" option with less powerful warheads for ballistic and cruise missiles launched from submarines.

Fan Jishe, a senior researcher of US studies at the Chinese Academy of Social Sciences, said the report is one of the recent signs that Washington is shifting its policy from cooperating with major world powers to competing with them.

The development of low-yield nuclear weapons may change the unwritten rule on the use of nuclear weapons as a last resort and suggests that the US may turn to nuclear weapons in conventional conflicts, which signals a retrogression regression and could result in disastrous consequences, he said.

Gregory Kulachi, a senior nuclear analyst with the Union of Concerned Scientists, a nonprofit science advocacy organization at the Massachusetts Institute of Technology, said the Trump administration's Nuclear Posture Review repeats one of the most pervasive misconceptions about the current state of the US nuclear arsenal: that it does not compare well with the nuclear arsenals of Russia and China.

"After a half-century of continuous incremental 'modernization', China's nuclear arsenal is smaller than the US nuclear arsenal was in 1950," Kulachi said in a Twitter post. "But the gap between China and the United States is too wide to argue the United States is lagging behind in any meaningful way."