US President Joe Biden has said he regrets using the term “illegal” during his State of the Union address to describe the suspected killer of Laken Riley.

Mr Biden spoke after Donald Trump, who is all-but-certain to be his rival in the autumn presidential election, blamed the President for her death at a rally attended by the Georgia nursing student’s family.

The President expressed remorse in an interview on Saturday after facing frustration from some in his party for the use of the term to describe people who arrived or are living in the US illegally.

He told MSNBC: “I shouldn’t have used ‘illegal’, it’s ‘undocumented’.”

The term was once common but is far less so today, particularly among Democrats who more fully embraced immigrant rights’ issues during Mr Trump’s presidency.

The death of Ms Riley, a nursing student, has become a rallying cry for Republicans, a tragedy that they say encompasses the Biden administration’s handling of the US-Mexico border amid a record surge of immigrants entering the country.

An immigrant from Venezuela who entered the US illegally has been arrested and charged with her murder.

Marjorie Taylor Greene
Marjorie Taylor Greene speaks before Donald Trump takes to the stage in Georgia (AP)

Mr Biden’s comments came in an interview with MSNBC’s Jonathan Capehart taped in Atlanta, where the President was meeting with small business owners and holding a campaign rally.

Across the state in Rome, Georgia, Mr Trump is expected to hammer Mr Biden on the border as well as his mispronunciation of Ms Riley’s name during the State of the Union address, according to excerpts released by his campaign before the speech.

“What Joe Biden has done on our border is a crime against humanity,” Mr Trump is set to say.

Mr Biden used the term on Thursday night during an exchange in which the President pressed Republicans in his address to pass a bipartisan border security deal that fell apart after Mr Trump opposed it.

US representative Marjorie Taylor Greene, a stalwart Trump ally, then shouted at the President to say Ms Riley’s name, adding she was killed “by an illegal”.

“By an illegal, that’s right,” Mr Biden responded immediately, before appearing to ask how many people are being killed by “legals”.

Jill and Joe Biden
President Joe Biden comes up behind first lady Jill Biden at a campaign rally in Atlanta (AP)

Speaking to Mr Capehart, Mr Biden said, “Look, when I spoke about the difference between Trump and me, one of the things I talked about in the border was his, the way he talks about vermin, the way he talks about these people polluting the blood. I talked about what I’m not going to do. What I won’t do. I’m not going to treat any, any, any of these people with disrespect.”

Trump campaign senior adviser Chris LaCivita attacked Mr Biden for apologising for his language and not to Ms Riley’s family.

“He should be apologising to the family as opposed to apologising for the word that he used which is an accurate description,” he told reporters before Mr Trump took the stage.

He blasted the response as “tone deaf” and a “pivotal moment” that highlights the candidates’ “two very distinct differences in approach on the border invasion”.

“There’s a clear difference,” he said. “One is sympathetic, coddling, and making excuses. And one wants to put a stop, put an end to it.”

Mr Biden’s expression of regret marked a shift from a day earlier, when Mr Biden had hesitated when asked by reporters if he regretted using the term.