New York (AFP) - Opening arguments are expected Tuesday in a highly anticipated defamation trial between US voting machine maker Dominion and Fox News that tests the extent of free speech rights for media in America -- even when broadcasting election falsehoods.

The proceedings, the start of which were pushed back by a day amid reports the conservative TV network is seeking a settlement, could become one of the most consequential libel cases ever heard in the United States.

It also threatens reputational and financial damage for Rupert Murdoch's 24-hour news behemoth and the media titan himself who is expected to be called to testify.

Dominion Voting Systems sued Fox News for $1.6 billion in March 2021, alleging the channel promoted Donald Trump's false claims that its machines were used to rig the 2020 presidential election that he lost to Joe Biden.

The company argues that Fox News aired the falsehoods while knowing they were untrue.

Dominion says the network began endorsing Trump's conspiracy because the channel was losing its audience after it became the first television outlet to call the southwestern state of Arizona for Biden, effectively projecting the Democrat would win the presidency.

Fox News denies defamation. It claims it was only reporting on Trump's allegations, not supporting them, and is protected by free speech rights enshrined in the First Amendment of the US Constitution.

The protection makes it difficult for plaintiffs to win defamation suits in the United States.

In pre-trial hearings, Delaware judge Eric Davis ruled that there was no question Fox aired false statements about Dominion.

For Dominion to win however, it would have to prove that Fox News acted with actual malice, a tough burden to meet and a bedrock of US media law since 1964.

Fox News employs some traditional news reporters, but the majority of its airtime is given to commentators, including in the several highly watched prime-time shows hosted by conservative thought leaders.

Embarrassing messages

Dominion's lawsuit has already proved embarrassing to Fox, while the Murdoch-owned Wall Street Journal reported that the channel was exploring ways to settle the case.

A settlement would mean 92-year-old Murdoch and star anchors, such as Tucker Carlson, would avoid having to take the witness stand in court.

Murdoch admitted in a deposition in the case that some on-air hosts had "endorsed" the false claim that the 2020 election was stolen from Trump.

But he denied that the network in its entirety had pushed the baseless claim, according to court documents filed by Dominion in February.

Dominion's lawyers also released a trove of internal Fox News communications in which some commentators expressed a dislike of Trump, despite praising him on air.

"I hate him passionately," Carlson said of the ex-president after his election loss.

Fox News has accused Dominion of "cherry-picking and taking quotes out of context."