The White House has insisted it was “very clear” that Joe Biden was referring to the New Zealand All Blacks rugby team when he made a mistaken reference to “the Black and Tans”.
The US President made the awkward gaffe in a County Louth pub during his tour of the island of Ireland.
Mr Biden appeared to confuse the name of the New Zealand rugby team with the contentious War of Independence-era police force during a speech at The Windsor in Dundalk on Wednesday night.
The 80-year-old paid tribute to his distant relative in the room, the former Irish rugby international Rob Kearney, who was a member of the team that famously beat New Zealand for the first time ever in a 2016 match played in Chicago.
"A hell of a rugby player," Mr Biden said, who "beat the Black and Tans".
Correcting himself after grimacing, Mr Biden continued: “Ah god. But, but it was when you were at Soldier Field, wasn’t it? Chicago.
“After it was all over he gave my brother, allegedly for me – but if it wasn’t I still took it – I still got the tie. I wore it with great pride.”
The Black and Tans is a name for part-time officers recruited to bolster Royal Irish Constabulary numbers, many of whom gained a violent reputation.
Asked if he realised his mistake, NSC senior director for Europe Amanda Sloat said: “It was clear what the President was referring to, it was certainly clear to his cousins sitting next to him.”
The White House said Mr Biden "had the time of his life" during his visit to County Louth, despite the unfortunate gaffe.
The US President's press secretary Karine Jean-Pierre said: "He had the chance to meet so many Irishmen and speak about the close ties between American and the Irish people."
Mr Biden is half way through a four-day tour of the island of Ireland.
He is expected to stay more on-script during heavily choreographed visits on Thursday, which includes making an address to the both houses of the Oireachtas, the Irish parliament.
He will visit President of Ireland Michael D Higgins at his official residence in Phoenix Park and will also have a meeting with Irish premier Leo Varadkar at nearby Farmleigh House.
At Farmleigh, the president will be invited to watch a sports demonstration by young gaelic games players.
After his parliamentary address on Thursday afternoon, Mr Biden will attend a banquet in his honour at Dublin Castle hosted by Taoiseach Mr Varadkar.
His first full day of engagements on Wednesday began in Northern Ireland and saw him deliver a keynote address in Belfast.
In his speech to Ulster University, Mr Biden expressed hopes of a return to power-sharing at Stormont, which the Democratic Unionist Party has to date refused to take part in over post-Brexit trading arrangements.
His visit north of the border came as the region marks the 25th anniversary of the landmark Good Friday peace accord, which ended three decades of violence known as The Troubles.
