Presumptive US Democratic presidential nominee Joe Biden has yielded to growing calls from within and outside his party to respond to a former aide’s allegation that he sexually assaulted her nearly 30 years ago.

The former vice-president will appear on MSNBC’s Morning Joe on Friday (local time) to address Tara Reade’s sexual assault allegation.

Mr Biden’s campaign has long denied Ms Reade’s assertions.

Tara Reade, who worked as a staff assistant in Mr Biden’s US Senate office from December 1992 to August 1993, has accused Mr Biden of pinning her against a wall in 1993 and reaching under her shirt and  skirt.

Mr Biden’s campaign has said the incident never occurred. Mr Biden himself has not previously addressed the allegation, nor has the former vice-president been questioned on the matter in recent interviews with national and local media.

Two more women corroborated part of Ms Reade’s allegation in interviews with Business Insider.

A Biden campaign spokesman declined to comment on Wednesday about the new sources or calls for Mr Biden to respond.

Reuters has not been able to independently confirm Ms Reade’s allegation and was also unable to reach Ms Reade or a representative for comment.

The New York Times said in a statement on Wednesday an investigation it conducted of the matter “made no conclusion either way”.

US Representative Alexandria Ocasio-Cortez, an influential liberal Democrat, said during an online forum this week that Ms Reade’s accusation deserves a fair examination.

Nina Turner, who was national campaign co-chair for Mr Biden’s former White House rival, Bernie Sanders, told Reuters on Wednesday that Mr Biden has to answer the question.

“It can’t appear that she’s being ignored just because it’s an inconvenient truth for certain people in the Democratic Party,” Turner said.

The Washington Post editorial board on Wednesday called on Mr Biden, 77, to speak about the allegations and release papers from the relevant period, when he was a senator from Delaware, in case those documents might include a complaint Ms Reade has said she filed over the incident.

Several prominent women on Mr Biden’s vice-presidential short list, such as Senators Kamala Harris and Amy Klobuchar and former Georgia state Representative Stacey Abrams, have stood by Mr Biden.

So has Senator Kirsten Gillibrand, another former presidential candidate, who has made aiding victims of sexual assault a centrepiece of her political career.

President Donald Trump’s re-election campaign has tried to turn the allegations into a liability for Mr Biden.

In a memo to the media on Wednesday, Trump campaign spokesman Tim Murtaugh said Mr Biden was seeking to shield himself from criticism by avoiding personally addressing Ms Reade’s allegation.

Mr Trump, 73, a Republican who will face Mr Biden in the November 3 general election, has been accused by more than a dozen women of sexual assault and misconduct over the years, allegations which he and his aides have consistently denied.

Ms Reade, 56, was one of eight women who last year came forward to say Biden had hugged, kissed or touched them in ways that made them uncomfortable, though none accused him of sexual assault.

She publicly accused him of the assault on a podcast in March.

At the time of the women’s statements last year about behaviour that made them uncomfortable, Mr Biden, who had yet to launch his presidential bid, released a video promising to be “much more mindful” of people’s personal space.

-with agencies