Roberts in an annual year-end report on the judiciary released just weeks before Republican President-elect Donald Trump takes office did not directly address what polling suggests has been a decline in public confidence in the judicial system broadly.

But Roberts said he felt compelled to highlight several areas of "illegitimate activity" that went far beyond informed criticism and debate concerning judicial rulings, which he said "threaten the independence of judges on which the rule of law depends."

Those areas of threats, he said, include a "significant" uptick in violent threats and online intimidation directed at judges, disinformation about court cases magnified by social media, and cyber threats posed by foreign state actors.

In the past five years, the U.S. Marshals Service has investigated more than 1,000 serious threats against federal judges, Roberts wrote. In some extreme cases, judicial officers have been issued bulletproof vests, he said.

He cited the risks of hackers stealing confidential information and of hostile foreign state actors spreading disinformation online, including by using bots to distort judicial decisions and "foment discord within our democracy."

Roberts also highlighted what he said were instances in the past few years in which "elected officials from across the political spectrum have raised the specter of open disregard for federal court rulings."

"These dangerous suggestions, however sporadic, must be soundly rejected," Roberts wrote.

Roberts, a member of the court's 6-3 conservative majority, did not specify which cases he was referring to, nor did he reference recent Supreme Court rulings that have set off political firestorms.

Those include its 2022 decision rolling back abortion rights or its July ruling granting Trump substantial immunity for actions taken in office in the now-dismissed 2020 election subversion criminal case he faced.

The report also did not discuss recent ethics controversies concerning gifts and travel received by members of the Supreme Court that have prompted investigations by Democratic lawmakers and calls for reforms.

Roberts acknowledged court rulings can "provoke strong and passionate reactions" and said criticism was not a threat, and that "public engagement with the work of the courts results in a better-informed polity and a more robust democracy."

But he said public officials "regrettably have engaged in recent attempts to intimidate judges -- for example, suggesting political bias in the judge's adverse rulings without a credible basis for such allegations."

"Public officials certainly have a right to criticize the work of the judiciary, but they should be mindful that intemperance in their statements when it comes to judges may prompt dangerous reactions by others," he wrote.