WASHINGTON – President Donald Trump and the White House on Tuesday continued to promote a baseless conspiracy theory about a woman’s 2001 death, ignoring her grieving widower’s plea for peace and putting renewed pressure on social media companies about the president’s use of their platforms.

Twitter issued a public apology to the family of Lori Klausutis, whose death Trump has repeatedly weaponized to attack MSNBC host Joe Scarborough. But the social media company rejected a request from her widower, Timothy Klausutis, to delete Trump’s conspiracy-laden tweets accusing Scarborough of a debunked murder plot, saying Lori Klausutis “deserves better.”

“We are deeply sorry about the pain these statements, and the attention they are drawing, are causing the family,” Twitter said Tuesday. “We’ve been working to expand existing product features and policies so we can more effectively address things like this going forward, and we hope to have those changes in place shortly.”

Later Tuesday, Twitter for the first time added labels to two Trump tweets that included misinformation about voter fraud, directing the president’s 80 million followers to “Get the facts” about the president’s false claims. The company did not take similar action against Trump’s tweets about Klausutis’ death.

Tuesday’s events reflected the pressure on Twitter and other social media companies to take responsibility for the false and misleading content they allow users to publish – a politically dicey proposition when one of the most prominent purveyors of such material is the president of the United States. Twitter, in resisting Klausutis’ request and doing nothing about the president’s tweets about the death of Lori Klausutis, effectively signaled that it was not applying the same standards to Trump that it does to average users – even as it puts a fact-checking label on his tweets, the first time the company has done so for a world leader.

Trump lashed out about the fact checks Tuesday evening on Twitter, accusing the company of stifling free speech and interfering in the upcoming presidential election.

Trump and his allies often complain that social media companies have an anti-conservative bias, putting political pressure on tech giants that are already facing scrutiny in Washington in areas such as antitrust.

Trump threatened earlier this month to take unspecified actions against tech companies, claiming without evidence that they are breaking the law.

“The Radical Left is in total command & control of Facebook, Instagram, Twitter and Google,” Trump tweeted on May 16. “The Administration is working to remedy this illegal situation. Stay tuned, and send names & events.”

The Wall Street Journal later reported that the White House is considering establishing a panel to review complaints of bias against conservatives.

Neither Trump nor his aides expressed remorse Tuesday about the president dragging Lori Klausutis into his feud with Scarborough, a former Republican congressman from Florida, despite her husband’s plea.

“I’m asking you to intervene in this instance because the President of the United States has taken something that does not belong him – the memory of my dead wife and perverted it for perceived political gain,” Timothy Klausutis wrote last week in a letter to Twitter chief executive Jack Dorsey. “My wife deserves better.”

Former vice president Joe Biden, the presumptive Democratic presidential nominee, said Twitter should take down Trump’s tweets.

“When things are patently not true they should say so,” he said during an interview with CNN.

Republican lawmakers largely remained silent.