US conservatives reprised some of their greatest hits on the opening day of their annual conference Thursday, as they offered multiple "culture war" grievances that framed government as the biggest threat to the American way of life.

Thousands of Republicans gathered at a plush riverfront hotel in the Washington suburbs to vet hopefuls weighing challenges to frontrunner Donald Trump in the race for the 2024 presidential nomination.

The Conservative Political Action Conference (CPAC) auditorium, which never appeared to be more than a quarter full, heard some serious discussion of the opioid epidemic, the rising threat from China and the immigration crisis.

But much of the debate focused on so-called "wedge" issues such as transgender athletes, "woke" education and perceived attacks on religious liberty as an array of firebrands aimed their sharpest broadsides at fellow Americans perceived as too progressive.

The event is set to feature three days of speeches from an array of right-wing A-listers -- including Brazil's recently-defeated leader Jair Bolsonaro -- although Trump's biggest primary rivals are staying away.

The 76-year-old's persistent polling strength has confounded his critics, showing him towering over potential rivals like former vice president Mike Pence and Florida Governor Ron DeSantis, seen as the strongest of the chasing pack.

Panelists at the event in Maryland's National Harbor hit all the right-wing sweet spots, calling for removal or jailing of numerous conservative betes noir, from President Joe Biden to former government scientist Anthony Fauci.

Texas Senator Ted Cruz said the recently-retired White House Covid-19 point man should be jailed over health curbs that had "ruined more lives than any bureaucrat in the history of our nation."

He accused Biden of not giving "a damn" about a recent Ohio train derailment that sparked fears of environmental contamination, and said the administration would have been quicker to help if the locals had been "transgender tech workers."

- 'Hunting the media' -
Conservative columnist and lawyer Kurt Schlichter echoed a favorite Trump grievance, accusing the press of being "the enemy" and joking about "hunting the media for sport."

In perhaps the most incendiary remarks of the day, Pennsylvania congressman Scott Perry warned liberals that they should be "quaking in fear" over the "firestorm" he wanted to unleash on them.

"They've got to be worried," he said. "They've got to be losing weight because they're not eating, because they're worried they're going to end up going to jail."

Senior House Republican Jim Jordan had set the tone from the opening minutes, bemoaning "cancel culture" and warning the audience that the Left "will come after you" if you disagree with them.

CPAC delegates will hear from more than 100 mostly pro-Trump speakers before the end of Saturday, including former cabinet secretaries and numerous far-right lawmakers.

Former UN ambassador Nikki Haley, the only high-profile Trump challenger to have announced her candidacy so far, is due to make her case Friday for a "new generation" of Republican leaders.

Attendees of the annual CPAC convention are almost all ardent Trumpists, although they speak glowingly of president Ronald Reagan.

Posters throughout the conference center decry gun restrictions, green energy measures, liberal school curriculums and big government.

Trump's keynote speech on Saturday is likely to reprise the "America First" agenda that swept him to power in 2016, taking in border security, gun rights, "woke" indoctrination and other red meat conservative issues.

Former secretary of state Mike Pompeo had been due to headline the opening day but organizers told AFP he had been rescheduled to 1:20 pm (1820 GMT) on Friday, without giving a reason for the change.