Dutchman De Vries had been under pressure for weeks after a disappointing start to his F1 career with the Italian squad.
Alongside fellow rookie Logan Sargeant, De Vries is the only driver yet to register points in 2023 as he struggled for pace compared to team-mate Yuki Tsunoda.
His cause wasn't helped by AlphaTauri underperforming with this season's AT04, which has left the team last in the constructors' championship after 10 races with just two points.
But Red Bull advisor Helmut Marko's patience with the former F2 and FE champion was wearing thin, giving De Vries repeated hints that his future was under immediate threat.
According to various media reports, including Dutch outlet De Telegraaf, AlphaTauri has now moved to replace De Vries in time for next week's Hungarian Grand Prix in Budapest.
It is not yet clear who will replace the 28-year-old at the Hungaroring, with third driver Daniel Ricciardo and Red Bull junior Liam Lawson appearing to be the two most serious candidates.
Ricciardo returned to the Red Bull family as a third driver this year after losing his McLaren drive one year before the end of his contract.
The 34-year-old Australian opted to take a sabbatical to recharge his batteries after a punishing stint with the Woking team but has been keeping race-ready and completed his first test with the current Red Bull RB19 on Tuesday.
AlphaTauri had previously been tipped to promote Lawson, who has had an impressive Super Formula campaign in Japan this year, but last month team boss Franz Tost suggested Ricciardo could be the team's best bet if its youngsters were not yet ready to step up.
“Of course, the team philosophy is to educate young drivers,” Tost said in Austria when asked if Ricciardo might be an option for his team.
“But if young drivers are not currently there – there are coming some good young drivers, [Ayumu] Iwasa is doing a good job, [Isack] Hadjar is doing a good job – but it's simply a little bit too early for them.
“I see them earlier or later in our team. But if the particular time is too early, then maybe we have to find another solution."
De Vries impressed Marko and AlphaTauri with a ninth-place finish on his F1 debut in last year's Italian Grand Prix, deputising for Alex Albon at Williams.
That led to talks with Marko in Graz to seal a contract for 2023, but subsequently he has only been handed 10 races to prove his worth.
De Vries took the F2 title in 2019 and then became a Formula E world champion in the 2020/21 season for Mercedes, having also been a valuable F1 simulator driver for the German manufacturer.
Neither the De Vries camp nor Red Bull were available for comment when approached by Motorsport.com.
