The head of the US Supreme Court warned that judges are being put at risk by rhetoric from politicians and the "threats of violence and murder."

Although Chief Justice John Roberts did not name names, his rare public warning came against a backdrop of constant verbal attacks led by President Donald Trump against courts blocking some of his more contentious policies.

Addressing a judicial conference in North Carolina on Saturday, Roberts cautioned against people "expressing a high degree of hostility to the court" or to judges who may be deemed "part of the problem" during more volatile political disputes.

"The danger, of course, is somebody might pick up on that, and we have had, of course, serious threats of violence and murder of judges just simply for doing their work," Roberts told the conference.

"I think the political people on both sides of the aisle need to keep that in mind," he said, stressing he did not believe the threats were associated more with Republicans or Democrats.

Since his return to the White House in January, Trump has launched fierce attacks on federal judges who have ruled against his executive orders, or blocked his efforts on the deportation of migrants or the slashing of the federal workforce.

The administration has expanded its withering attacks on judges. In April the FBI arrested a Milwaukee judge, Hannah Dugan, for trying to help an individual evade Immigration and Customs Enforcement agents.

The White House has been accused of defying some court orders it disagrees with, accusations the administration denies.

Amid multiple standoffs between the Trump White House and federal courts, the president and some Republican lawmakers have called for the impeachment of judges who have temporarily paused Trump's orders to cut government spending or ramp up deportations.

He has blasted federal judges as "monsters" who suffer from a "sick" ideology and want the United States to "go to hell."

As recently as Friday he lashed out at "radical left judges" who he said pose a "grave threat to democracy" for seeking to curb the president's powers.

Violence and threats against judges in the United States have risen in recent years. A man in 2022 was arrested for threatening to kill Supreme Court Justice Brett Kavanaugh.

In 2023 a Maryland judge was murdered, while a judge in Kentucky was shot and killed in his courthouse in 2024.

Roberts said people from across the political spectrum should be mindful of the dangers.

"Threatening the judges for doing their job is totally unacceptable," he said.

In March, Roberts clashed in extraordinary fashion with the executive branch when he rebuked Trump for seeking the impeachment of US District Judge James Boasberg, who had issued an order blocking deportation flights that Trump was carrying out.

Trump had blasted Boasberg as a "Radical Left Lunatic."