North Korean leader Kim Jong-un, center, inspects the country's nuclear weapons research institute as well as a weapons-grade uranium enrichment production facility in this photo released by the North's official Korean Central News Agency, Sept. 13. Yonhap

An updated U.S. nuclear employment strategy calls for the United States to be able to deter threats from North Korea, China and Russia "simultaneously" during peacetime, a crisis and in conflict, a Pentagon report showed Friday.

On Thursday, Defense Secretary Lloyd Austin submitted to Congress the "491 Report" describing the nuclear employment strategy in reflection of an unclassified description of nuclear employment guidance issued by President Joe Biden earlier this year, according to the Pentagon.

The updated strategy directed the U.S. government to have the capability to simultaneously address threats from the three countries, noting that "growing collaboration and collusion" between Pyongyang, Beijing, Moscow and as well as Tehran make the global security situation "even more challenging."

"Updated elements of the Guidance evolved from prior iterations by ... directing that the United States be able to deter Russia, the PRC, and the DPRK simultaneously in peacetime, crisis, and conflict," the report said.

PRC and DPRK stand for the official names of China and North Korea, the Republic of China and the Democratic People's Republic of Korea.

In part of the report expounding the security environment, it underscored Pyongyang's continued advances in its nuclear and missile programs.

"The Democratic People's Republic of Korea also continues to expand, diversify, and improve its nuclear, ballistic missile, and non-nuclear capabilities," it said.

The report pointed out that Russia poses an "acute" threat with its large, modern, and diversified nuclear arsenal of strategic and theater-range weapons as well as its pursuit of novel nuclear systems.

It also said that China has embarked on an "ambitious" expansion, modernization, and diversification of its nuclear forces and established a nascent nuclear triad.

The report came after senior U.S. officials warned that adjustments to the number of deployed U.S. nuclear capabilities may be necessary if America's potential adversaries continue down the current trajectory of growing nuclear arsenals.

Nuclear threats from the North, China and Russia have come into renewed focus as Russia has been deepening its cooperation with both North Korea and China in the midst of its diplomatic isolation caused by the protracted war in Ukraine.

In a telling sign of their burgeoning cooperation, Russia and the North signed a "comprehensive strategic partnership" treaty during their summit in June. Russia and China have also boasted their "no limits" partnership, while Washington has decried Beijing for its support for Russia's defense industrial base.

Updating U.S. nuclear employment guidance is "routine and critical to ensuring that U.S. nuclear forces, plans, and posture evolve to maintain the U.S.' ability to deter adversaries, assure allies and partners, and achieve national objectives if deterrence fails," the Pentagon said in a press release. (Yonhap)