WASHINGTON — Joseph R. Biden Jr. will publicly address an allegation of sexual assault for the first time in an appearance on morning television on Friday, after weeks of silence on the issue that had prompted frustration from Democrats and attacks from Republicans seeking to weaken him for a general election contest against President Trump.

Mr. Biden will discuss the allegation on “Morning Joe” on MSNBC, according to a Twitter post from the network. The decision followed intensive discussions in the Biden campaign about how to more forcefully confront the allegation.

The planned appearance came as scrutiny of the allegation intensified along partisan lines on Capitol Hill on Thursday. Nancy Pelosi, the House speaker and the Democratic Party’s highest-ranking officeholder, expressed support for Mr. Biden’s presidential bid, while Republicans weaponized the accusation to attack congressional Democrats as hypocritical.

The allegation Mr. Biden will address was made by a former aide in his Senate office, Tara Reade, who has said Mr. Biden assaulted her in a Senate building in 1993. Mr. Biden’s campaign has said the accusation is not true, but the former vice president himself had not addressed the issue publicly. His silence has raised questions among some Democrats about the agility of his campaign operation and its ability to navigate what is widely expected to be a heated and deeply divisive presidential campaign this fall.