The lawsuit -- which names Hegseth, the Defense Department, Navy Secretary John Phelan and the department he heads -- said their actions "violate numerous constitutional guarantees and have no basis in statute. They should proceed no further."

Kelly, a decorated Navy veteran and former astronaut, asked the court to declare a censure letter placed in his file as well as efforts to potentially reduce his military rank in retirement -- and thus his pension -- to be "unlawful and unconstitutional."

The Pentagon is "aware" of the lawsuit but "does not comment on ongoing litigation," an official said in response to a question from AFP.

Kelly later addressed the lawsuit in remarks on the Senate floor, defending the comments that drew the ire of the defense secretary.

"Pete Hegseth is now coming after what I earned through my 25 years of military service, in violation of my rights as an American and as a retired veteran and as a United States senator," Kelly said.

- 'Restated the law' -

"I simply restated the law: that service members must refuse illegal orders. Somehow, restating the law is now against the law, according to Pete Hegseth," the senator added.

Hegseth announced the measures against Kelly last week, saying the senator and five other lawmakers with military or intelligence service backgrounds "released a reckless and seditious video that was clearly intended to undermine good order and military discipline."

In the November video, the lawmakers said President Donald Trump's administration was "pitting our uniformed military and intelligence community professionals against American citizens."

"Right now, the threats to our constitution aren't just coming from abroad, but from right here at home," they said, adding: "You can refuse illegal orders."

The lawmakers in the video did not specify which orders they were referring to, but the Trump administration has come under fire over its use of US forces both at home and abroad.

Inside the United States, Trump has ordered the National Guard into multiple US cities -- often against the wishes of local officials, who have responded with legal challenges -- claiming the deployments are necessary to maintain order against sporadic, sometimes violent protests.

And outside the country, Trump has ordered a series of strikes on alleged drug-smuggling vessels in the Caribbean Sea and eastern Pacific Ocean that have left more than 100 people dead since early September -- actions that experts say amount to extrajudicial killings.

This month, he ordered US forces into Venezuela, where they seized then-president Nicolas Maduro and brought him to the United States to face a New York court.