​Liverpool manager Jürgen Klopp insists Trent Alexander-Arnold must keep improving if he wants to stay as Gareth Southgate's first-choice right-back with England.

The 20-year-old has made six appearances for the Three Lions since his Liverpool debut in 2016, stepping out with England's senior side just before the World Cup in a 2-0 win over Costa Rica at Elland Road.

Despite widely being considered as one of the best defenders in Europe already, Klopp insists Alexander-Arnold won't have a place in that national team guaranteed as England have a number of different options at right-back.

Trent Alexander-Arnold

"He had [difficult] moments already, it is not that his career went just like this [straight up]," Klopp said, quoted by The Mirror. "He had moments and will have [more]. He is a very young lad.

"I have no clue why Gareth made the decision but I don’t think Kyle [Walker] is that old to not have a chance anymore.

"It is a sign that England have a couple of really good opportunities with young players in Aaron Wan-Bissaka and Trent.

"Last year Kieran Trippier played there in the World Cup and was providing wonderful crosses, so there are obviously a couple of options.

"That creates a situation for a manager where you have to make a decision.

"But that doesn’t mean that from now on Trent is the No1 full back for the next 20 years. He has the skills to do so, but there are a lot of things you have to make sure."

Alongside Alexander-Arnold in England's most recent squad are Manchester United's Aaron Wan-Bissaka and Kieran Tripper, who has had a good start to life since his move to Atlético Madrid.

Alexander-Arnold's teammate Joe Gomez, who can be used as a right-back, has also been included in Southgate's squad ahead of Euro 2020 qualifiers against Bulgaria and Kosovo, which includes four potential debutants.