The report from the Strategic Posture Commission comes amid tensions with China over Taiwan and other issues and worsening frictions with Russia over its invasion of Ukraine.
A senior official involved in the report declined to say if the panel's intelligence briefings showed any Chinese and Russian nuclear weapons cooperation.
"We worry ... there may be ultimate coordination between them in some way, which gets us to this two-war construct," the official said on condition of anonymity.
The findings would upend current U.S. national security strategy calling for winning one conflict while deterring another and require huge defense spending increases with uncertain congressional support.
"We do recognize budget realities, but we also believe the nation must make these investments," the Democratic chair, Madelyn Creedon, a former deputy head of the agency that oversees U.S. nuclear weapons, and the vice chair, Jon Kyl, a retired Republican senator, said in the report's preface.