Andretti Autosport is unlikely to expand into the TUDOR United SportsCar Championship next year, after an attempt to field a pair of HPD ARX-04b cars has fallen through.

Team boss Michael Andretti confirmed the news Sunday morning at the Milwaukee Mile, site of today’s Verizon IndyCar Series race.

“It doesn’t look like that’s going to happen. It unfortunately fell through, so we’re a little disappointed with that,” Andretti said about the team’s proposed re-entry into sports car racing.

While having been part of the factory Acura LMP2 program in the American Le Mans Series in 2007-08, the Indianapolis-based team had been working towards a return to prototype competition with HPD’s new closed-top P2 car.

It’s unclear on the exact reason for the program not going forward but is believed to be budget-related.

Andretti Autosport’s no-go leaves a significant question mark over the size of the P2 grid in the TUDOR Championship next year, with both the front-running Extreme Speed Motorsports and OAK Racing squads having yet to confirm 2015 programs.

While ESM has committed to the four-round Tequila Patron North American Endurance Cup next year, the Scott Sharp-owned squad could contest select rounds of the FIA World Endurance Championship in lieu of a full season in the States.

The France-based OAK squad, meanwhile, may also not return depending on the level of customer interest and sales of its Morgan and Ligier LMP2 cars in the U.S.

It’s understood that OAK’s parent company, Onroak Automotive, is close to finalizing the sale of a Ligier JS P2 to Krohn Racing, but that too would only likely run the TPNAEC rounds.

While both Rahal Letterman Lanigan Racing and Schmidt Peterson Motorsports have expressed interest in expanding into the Prototype class with P2-based machinery, a green light has yet to be given on either programs, which are also dependent on outside funding.

Tony DiZinno contributed to this article