Mauricio Pochettino said Friday that leaving his role as USA boss to take charge of Manchester United was "one of the most difficult" decisions of his career as he prepares for one of football's toughest jobs.

The 54-year-old Argentine fought back tears as he bade an emotional farewell to US football, hours after the Premier League giants announced he would replace the sacked Michael Carrick.

The former Tottenham, Paris Saint-Germain and Chelsea boss will take up his new position on November 18, with a monumental task ahead of him.

United have made their worst start to a domestic campaign in 40 years and are languishing in the Premier League relegation zone during the current international break.

Pochettino is understood to have signed a two-and-a-half-year deal at Old Trafford, taking him through to the end of the 2028/29 season.

"We learned a lot from you all, from this amazing country," Pochettino told a media conference in Fayetteville, Georgia. "I think this was one of the most difficult decisions of (my) career."

Pochettino, who led the USA to the last 16 at this year's World Cup, will oversee back-to-back CONCACAF Nations League matches against Haiti on Saturday and next Tuesday before leaving for England.

He said he had not considered a possible return to the Premier League when he signed a contract extension with US Soccer in August, but added the opportunity to join United was too good to turn down.

"I never said I wanted to go back in the Premier League," he said. "Not too many opportunities can happen in your career with a side like Manchester United. That is difficult to turn down when it arrives."

US Soccer CEO and secretary general JT Batson said Pochettino had left a lasting legacy through his "leadership, professionalism and commitment to our players and culture".

The federation is reportedly set to receive around $10 million in compensation, plus more to cover the departure of Pochettino's coaching staff.

ATTACKING FOOTBALL

"Pochettino has consistently performed at the highest level of football across multiple leagues," the club added.

The 20-time English champions are one of the giants of world football but have largely been also-rans since Alex Ferguson retired in 2013.

Pochettino is the eighth permanent manager tasked with returning the Red Devils to former glories.

He started his Premier League managerial career with Southampton before joining Tottenham, where he never finished lower than fifth during his five full seasons in charge and also reached the 2019 Champions League final.

Pochettino claimed the first trophies of his managerial career with PSG, collecting the 2021 French Cup and 2022 Ligue 1 title, but did not see out his contract in Paris.

He returned to the dugout at Chelsea in 2023 but only lasted one season.

The former Argentina defender, who has been linked with the United job on several previous occasions, faces a baptism of fire at the home of fierce rivals Liverpool on November 22.

He must unite a club that is deeply divided on and off the pitch.

United captain Bruno Fernandes was dropped last month after he criticised Carrick's tactics and Lisandro Martinez took a public swipe at the United hierarchy over a lack of investment.

Angry fans vented their frustration at the club's ownership following the sacking of the popular Carrick, who won multiple trophies as a player.

Despite fierce and persistent protests over two decades, the US-based Glazer family still hold a majority stake in United, which Malcolm Glazer bought via a leveraged takeover in 2005, saddling the club with huge debts.

Any hopes the arrival of British billionaire Jim Ratcliffe as a minority owner in 2024 would signal a new dawn have since faded.

Carrick issued an emotional statement Friday wishing United "nothing but success", adding that his love for the club "never dies".