Former Vice President Joe Biden gave Donald Trump a nickname on Saturday while dismissing the idea of getting into a 'mud-wrestling match' with the president if they go head-to-head for the White House in 2020.

Biden told donors in South Carolina that he knows Trump is 'going to go after me and my family' but pledged to answer the president 'directly' without name-calling.

Then he called him 'a clown,' and later added 'no-good S.O.B.,' while hinting that there are more nicknames to come.

Biden also flubbed an attack on Trump's foreign policy performance, beginning to announce that Margaret Thatcher had invited him to speak in the United Kingdom about American foreign policy – before correcting himself and correctly naming Theresa May as the British prime minister.

'Margaret Thatcher – um, excuse me, Margaret Thatcher, Freudian slip,' Biden said as laughter rang out. 'But I knew her too.'

Former Vice President Joe Biden pledged Saturday night in South Carolina that he wouldn't get in the muc with President Donald Trump during a protracted White House campaign, and then called him a 'clown' and a 'no-good S.O.B.'

President Trump has called Biden 'Sleepy Joe' and 'Crazy Joe' in the past, and appears eager to square off against one of the only two people in a 22-contestant Democratic field who is older than he is

Biden is conducting a two-day swing through South Carolina, which will hold the first presidential primary in the South at the end of next February

After a moment to think, the 76-year-old Democrat continued: 'The Prime Minister of Great Britain Theresa May.'

Thatcher died in 2013, more than two decades after leaving office.

BIden said May had asked him: 'We still have a special relationship between [the] United States and England?'

'I said, jokingingly, "It’s an Irishman telling you, yeah",' he said.

Biden has drawn cautious support from the Democratic Party establishment amid concerns about his advancing age. He launched his third presidential campaign ten days ago.

His first run at the White House, in 1988, ended in disaster after critics found that he had plagiarized portions of a speech from Neil Kinnock, the British Labour Party leader who was Thatcher's most outspoken domestic foe at the time.

Biden raised May's name on Saturday after claiming that 'at least 14 heads of state' have contacted him during Trump's time in office, 'including very, very conservative heads of state.'

The United Kingdom's head of state is Queen Elizabeth II.

'I think, whether I’m right or not, I know as much about American foreign policy than anyone around,' he said, 'including even maybe [Henry] Kissinger. I say that because I’ve been doing it my entire adult life. I’ve literally had a chance to meet virtually every major world leader.'

Biden spent 36 years in the U.S. Senate before the eight years he served as Barack Obama's vice president.

Biden claimed Saturday that British Prime Minister Theresa May invited him to the UK to speak about American foreign policy, but couldn't come up with her name

Instead of May, Biden cited the late Prime Minister Margaret Thatcher, who left Parliament in 1990 and died in 2013

His longstanding feuds with Trump are likely to get more intense as 2019 heads toward 2020.

The president has already branded him 'Sleepy Joe' and 'Crazy Joe.'

Biden claimed Saturday that he wanted to keep the political discourse at a more civilized level.

'The only place he has any confidence is in the mud. The only thing he doesn’t know how to respond to is issues and specifics,' he said of the president.

Asked if he would pick his own derogatory nickname for Trump, he responded: 'There’s so many nicknames I’m inclined to give this guy''

'You can just start with "clown".'

Later, as he warned that the president and his surrogates would likely attack his family members during a protracted campaign, he called Trump a 'no-good S.O.B.'

But he admitted regret over a pair of previous boasts that if the two were in high school he would have taken Trump behind the gym and 'beat the hell out of him.'

'Well guess what? I probably shouldn’t have done that,' Biden said.

Biden took selfies with people in the crowd after a campaign event in Columbia, South Carolina on Saturday

Trump has blasted Biden with nicknames that, so far, are less aggressive than the 'no-good S.O.B.' label the former vice president gave him on Saturday

Biden admitted Saturday that he shouldn't have suggested last year that he would have liked to beat up Trump in high school – a boast that brought this counter-punch from the president at the time

'I don’t want to get it down to that level. The presidency is an office that requires some dignity.'

At the time, Trump pushed back hard on Twitter.

'Crazy Joe Biden is trying to act like a tough guy,' he wrote in March 2018. 'Actually, he is weak, both mentally and physically, and yet he threatens me, for the second time, with physical assault.'

'He doesn’t know me, but he would go down fast and hard, crying all the way. Don’t threaten people Joe!'

Biden is conducting a two-day swing through South Carolina, which will hold the first presidential primary in the South at the end of next February.

Saturday's fundraised cost between $1,000 and $2,800 per person to attend.