"It is the theme of every autocrat who ever seized power or tried to hold onto it," he argued. McRaven, who had a distinguished military career as a Navy SEAL and oversaw the raid that killed Osama bin Laden, has become an outspoken critic of Trump.

Retired US Navy Adm. William McRaven, the Navy SEAL who oversaw the raid that eliminated the terrorist leader Osama bin Laden in 2011, accused President Donald Trump of undermining not only the United States Postal Service but every major US institution.

"Today, as we struggle with social upheaval, soaring debt, record unemployment, a runaway pandemic, and rising threats from China and Russia, President Trump is actively working to undermine every major institution in this country," McRaven wrote in an op-ed article published in The Washington Post on Sunday.

McRaven argued that the president was planting "the seeds of doubt" in the minds of the American people about the efficacy of institutions and groups including the intelligence community, law-enforcement agencies, the media, the military, the courts, election officials, medical experts, and postal workers.

"If Americans stop believing in the system of institutions, then what is left but chaos and who can bring order out of chaos: only Trump," he wrote. "It is the theme of every autocrat who ever seized power or tried to hold onto it."

The US Postal Service has emerged as a focal point during the coronavirus pandemic and ahead of the presidential election. Trump has claimed, without evidence, that voting by mail will lead to extensive voter fraud and has suggested withholding funding from the Postal Service, sparking concerns that he is stoking fears about voting systems that have been free of widespread fraud.

"Our institutions are the foundation of a functioning democracy," McRaven wrote. "While they are not perfect, they are still the strongest bulwark against overzealous authority figures."

He added: "As Trump seeks to undermine the US Postal Service and stop mail-in voting, he is taking away our voice to decide who will lead America. It is not hyperbole to say that the future of the country could depend on those remarkable men and women who brave the elements to bring us our mail and deliver our vote."

McRaven has emerged as an unlikely and outspoken critic of the president. Last fall, the retired admiral wrote an op-ed article in The New York Times with the headline "Our Republic Is Under Attack From the President."

"If this president doesn't demonstrate the leadership that America needs, both domestically and abroad, then it is time for a new person in the Oval Office," he wrote in that op-ed article.

McRaven, who has written bestselling books on leadership including "Make Your Bed: Little Things That Can Change Your Life ... and Maybe the World" and "Sea Stories: My Life in Special Operations," served in the US military for 36 years before his retirement in 2014. He was the chancellor of the University of Texas system for three years.