Earlier on Friday, Tech3 announced that it would swap eight-time podium finisher Espargaro in favour of Moto2 championship leader Acosta, while Augusto Fernandez would retain his seat.
It ends a months-long rider logjam for KTM, having had five riders contracted to four seats for 2024.
Espargaro did sign a two-year deal to return to KTM with the GasGas-branded Tech3 squad for 2023.
In a Tech3 and GasGas statement released earlier today, it said Espargaro mutually agreed with the team to step aside into a test rider role to make way for Acosta.
In his own statement issued on social media, Espargaro confirmed this and says it was done as part of a long-term vision to make the Pierer Mobility Group “the reference in MotoGP”.
“Hi everyone, as you know I'm not a social media fan, but as I'm receiving a lot of messages of encouragement/support for the Pierer Mobility Group's news regarding our future, I wanted to clarify a few things,” Espargaro began.
“First of all, thank you very much for all the messages. Even so, I want to tell you that it has not been a unilateral decision - on the contrary!
“It is true that I would have liked to continue racing full-time in MotoGP because I think I still have the speed to be among the best.
“But the truth is that the step aside that I will take next year by joining the test team and making several wildcards is the result of an understanding between the two parties given the contractual problems in which the group has at the moment and thinking of a long-term collaboration to make Pierer Mobility Group the reference in the MotoGP World Championship!
“Still [I have] many races left this year and also in the future, and as I am one of those who believe that unity is strength, we will stick together to achieve a memorable end of season! Thank you very much!”
Espargaro missed the opening eight rounds of the season after suffering serious injuries in a crash during FP2 for the Portuguese Grand Prix in March.
Since returning to action at the British GP, he has achieved a best of sixth in the sprint race in Austria.
KTM attempted to solve its logjam by expanding into the grid slots vacated by Suzuki, but was denied expansion by Dorna Sports as the commercial rights holder wants to keep those reserved for a new factory entrant.
