The move was announced by the 2019/20 P2 champion team in the wake of confirmation on Friday that there will be no P2 class in the world championship next season.
United, which is co-owned by McLaren Racing boss Zak Brown, will make its first full-season IMSA assault with a pair of ORECA-Gibson 07s while continuing to compete in both the European and Asian Le Mans Series next year.
Team boss Richard Dean explained that the “redirection of our entire WEC team” to IMSA was for the “foreseeable future”.
He revealed that competing in IMSA full-time was a long-held ambition for United after taking in a total of eight races in the North American series since 2018.
“It’s easy for us to say that we have always wanted to do a full season in IMSA right now, but it’s true,” he told Autosport.
“This has given us the necessary kick up the backside to go and do it.”
Dean described the disappearance of P2 from the WEC as “a shame”, but said he understood the decision made by series organisers the FIA and the Automobile Club de l’Ouest.
“It is as a direct result of the success of Hypercar, which for the sport as a whole can only be a good thing," he said.
There will be no room for P2 as the Hypercar field grid expands to 20 or more cars and the new LMGT3 class takes over from GTE Am.
Dean insisted that United still has ambitions to graduate to the premier class of the WEC at some point in the future.
“Absolutely, we still want to race in Hypercar; the ambition hasn’t changed,” he said.
“We are still working on it and pushing hard, but there has got to be a door that’s unlocked if it is going to happen.”
United is not underestimating the challenge that will be presented by racing in IMSA, according to Dean.
“We have won races in the WEC, ELMS and Asian series every time we have entered cars, but it would be totally wrong to assume that we are going to do the same in IMSA,” he said.
“It is very different and we are not underestimating the challenge.”
Dean confirmed that United has yet to sign any drivers for its IMSA programme.
He also reaffirmed United’s intention to make a bid for two of the 15 grid slots to be reserved for P2 competitors at the Le Mans 24 Hours next year.
It will continue in the ELMS with a programme focussed on LMP2 and is also aiming to continue in both P2 and LMP3 in the expanded 2024 Asian series.
United first raced in IMSA in its own right at the 2018 Daytona 24 Hours when it fielded a Ligier-Gibson JS P217 for Fernando Alonso, Lando Norris and Phil Hanson.
Its most recent Stateside programme came with an ORECA at last year’s Daytona and Sebring enduros.
United also entered cars in two of the big US enduros in 2011 in conjunction with other teams.
It joined forces with Michael Shank Racing to field a Riley-Ford MkXX at Daytona when it was a round of the Grand American Sportscar Series and then OAK Racing to run a Pescarolo-Judd/BMW 01 LMP2 at the American Le Mans Series 1000-mile enduro at Road Atlanta.
