China on Wednesday said it was “seriously concerned” after a report alleged the United States recently approved a secret plan to shift some of the focus of its nuclear strategy away from Russia to deal with Beijing's nuclear weapons buildup.

In a report late Tuesday, The New York Times reported that U.S. President Joe Biden in March approved a new “nuclear employment guidance,” a highly classified document outlining how the U.S. would use nuclear weapons in a potential conflict.

The report said the document, updated every four years, reorients U.S. nuclear deterrent strategy to deal with China’s massive expansion of its nuclear arsenal. The document also orders U.S. forces to prepare for the possibility of “coordinated nuclear challenges” from China, Russia, and North Korea, according to the report.

Asked about the report during a press briefing Wednesday, a Chinese foreign ministry spokesperson accused the United States of “peddling the China nuclear threat narrative” and “finding excuses to seek strategic advantage.”

"China is seriously concerned about the relevant report, and the facts have fully proven that the United States has constantly stirred up the so-called China nuclear threat theory in recent years," said Chinese foreign ministry spokesperson Mao Ning.

Russia has not responded to the report.

For decades, U.S. nuclear policy has been primarily focused on Russia, the only other country with comparable nuclear weapons capabilities.

However, U.S. officials have increasingly warned that China’s nuclear buildup under President Xi Jinping is proceeding faster than previously expected.

In an unclassified document released late last year, the Pentagon estimated that the Chinese military had more than 500 operational warheads in its arsenal and will have more than 1,000 warheads by 2030.

That compares to the United States, which possesses a nuclear stockpile of about 3,700 active warheads, according to estimates compiled by the U.S.-based Arms Control Association.

Russia has roughly 4,380 nuclear warheads, including about 1,550 on strategic delivery systems, according to estimates cited by the group.

Given those numbers, Russia remains the “major driver” behind U.S. nuclear strategy, said Daryl G. Kimball, the director of the Arms Control Association, in a post on social media site X.

The Times report overstates the changes outlined in the U.S. nuclear weapons guidance document, according to Kimball, who insisted there has been no reorientation away from Russia toward China.

“Despite China’s nuclear expansion, Russia’s arsenal significantly exceeds that of China’s - even after Xi’s ambitious plan is complete. Until that changes, focus will remain on Russia’s arsenal,” said Hans Kristensen, director of the Nuclear Information Project at the Federation of American Scientists.

“But planning against China is increasing, as reflected in the document,” Kristensen added in a post on X.

U.S. officials have publicly referred to the nuclear weapons document at least twice, without offering much detail on its contents.

In June, Pranay Vaddi, the White House National Security Council’s senior director for arms control and nonproliferation, said the new guidance “emphasizes the need to account for the growth and diversity” of China’s nuclear arsenal, as well the need to deter Russia, China, and North Korea simultaneously.

According to Vaddi, the U.S. will continue to pursue nuclear arms restraints with Russia and China, but “without a change in the trajectory that Russia, [China], and North Korea are on,” the U.S. “will need to continue to adjust our posture and capabilities to ensure our ability to deter and meet other objectives going forward.”

Vipin Narang, an MIT nuclear security specialist who until recently focused on nuclear policy in the Pentagon, said earlier this month that Biden “recently issued updated nuclear weapons employment guidance to account for multiple nuclear-armed adversaries, and, in particular, the significant increase in the size and diversity of [China’s] nuclear arsenal.”

“It is our responsibility to see the world as it is, not as we hoped or wished it would be,” said Narang. “It is possible that we will one day look back and see the quarter century after the Cold War as ‘nuclear intermission’.”

U.S. and Chinese officials both frequently speak of the dangers of nuclear war, but efforts to hold dialogue on the issue have failed.

Last year, U.S. and Chinese officials agreed to negotiations on nuclear non-proliferation and arms control, ahead of a meeting between Biden and Xi. But China suspended the talks last month, citing U.S. arms sales to the self-ruled island of Taiwan, which Beijing claims as its own.

Many analysts are also concerned about growing military and diplomatic cooperation between Russia and China. In 2022, Xi and Russian President Vladimir Putin agreed on a “no-limits” partnership and have recently expanded joint military exercises and other cooperation.

Earlier this year, Russia also restored a Cold War-era mutual defense treaty with nuclear-armed North Korea and hinted at further defense cooperation.

Since invading Ukraine in 2022, Putin has repeatedly issued thinly veiled threats about using nuclear weapons against Western-backed forces there.