By Will Butcher

Mamadou Sakho’s future at Liverpool has plunged into doubt after being told to join left-back Brad Smith on a plane home from the club’s US tour, according to a report.

Sakho had been receiving treatment on an achilles injury that is likely to rule him out for the start of the season, and was booked on the same overnight flight Monday as Bournemouth-bound Smith.

However, the Liverpool Echo have reported that there were concerns over the former Paris Saint-Germain defender’s attitude at the Reds’ California training base, which could have contributed to Klopp’s decision.

The 26-year-old joined full-back Smith on the plane as the Australia international flew home to tie-up a £6million move to The Cherries.

The 22-year-old, who has three years remaining on his Anfield deal, was given the green light to fly home after Liverpool accepted a bid from their Premier League rivals.

Liverpool officials have briefed that Sakho has joined Smith but refused to comment on the reason behind former Borussia Dortmund manager Klopp’s decision.

The 28-time France international is expected to return to Liverpool’s training ground and will have to watch on as his side face Chelsea, AC Milan and Roma in the next coming days.

Sakho’s first-team position is currently under threat after Klopp has confirmed the centre-back signings of Schalke’s Joel Matip and Estonia captain Ragnar Klavan.

Liverpool’s number three signed for the Merseyside club three years ago for around £18million, and featured 34 times for The Reds last season.

The defender, who hasn’t played since April 20, missed out on the Liverpool’s Europa League final against Sevilla, as well as France’s Euro 2016 campaign after the World Anti-Doping Agency (WADA) alleged that he had consumed a prohibited ‘fat burner’.

In other Liverpool news, Klopp’s move to sign this promising Leicester defender is edging closer.