Republican Senator Ted Cruz apologised on 4 June after making a joke about Joe Biden just days after the vice president lost his son Beau Biden to brain cancer.

"It was a mistake to use an old joke about Joe Biden during his time of grief, and I sincerely apologise," Cruz wrote on his Facebook page. "The loss of his son is heartbreaking and tragic, and our prayers are very much with the Vice President and his family."

It was a mistake to use an old joke about Joe Biden during his time of grief, and I sincerely apologize. The loss of his...

Posted by Ted Cruz on Wednesday, June 3, 2015

At a Republican dinner in Howell, Michigan on Wednesday (3 June) night, the presidential candidate said: "Vice President Joe Biden. You know the nice thing? You don't need a punchline. I promise you it works. The next party you you're at, just walk up to someone and say, 'Vice President Joe Biden' and just close your mouth. They will crack up laughing."

Following the event, Cruz told reporters that the Saturday death of 46-year-old Beau Biden was "heartbreaking and tragic" and said he was praying for the vice president and his family, according to NBC News.

When the candidate was asked by Detroit News reporter Chad Livengood why he would make the joke, he walked away before commenting.

Cruz faced immediate backlash after video of his joke and subsequent interview went viral. Even after apologising, Cruz was met by criticism on his Facebook page.

"Too little - too late. The ability to think ahead is what is needed in a leader," Gail Ziegler wrote.

Nick Pealy added: "Sorry, but you've never shown any sense of judgement on anything. This demonstrates, once again, that you have no moral core."

However, Cruz did have the support of some on social media. "Well people make mistakes, at least you know when to admit as a man that you have made a mistake. Bill Clinton just lied to America when he made his mistake," wrote Dion Ruiz.