WASHINGTON — While some Air Force officials have begun thinking about replacing the A-10 Warthog, including a new proposal that would involve buying two aircraft types, the service's top civilian leader on Tuesday questioned the affordability of such an endeavor.

During a Defense One event Tuesday morning, Air Force Secretary Deborah Lee James said she had not been briefed on any potential options or an acquisition strategy related to a new close air support (CAS) aircraft, dubbed A-X. One of the options the service is perusing is the purchase of two CAS aircraft meant to augment and eventually replace the A-10.

"So far I have read about this in the news. I have not actually seen a proposal on any of this that has come forward to me. So it sure is pre-decisional. It hasn't been decided on," she said. "Where would we get the money? Not at all clear to me."

The Air Force met with aviation experts last Wednesday to discuss a proposal that would involve buying two close air support aircraft, Aviation Week first reported last week.

The first, called OA-X, would support the A-10 in near-term operations, not replace it outright. The service would likely use an existing, off-the-shelf design like the Beechcraft AT-6 or Embraer A-29 Super Tucano to cheaply carry out CAS missions in low-threat environments. A second aircraft, called A-X2, would then be fielded to replace the Warthog and operate in medium-threat environments.

Neither of those proposals have yet been funded through the budget process because the service is still going through its requirements-generation process, a fact reiterated by James.

"I'm just going to wait to see whether this proposal is to come forward. Of course the money is the important thing," she added, pointing out that the Air Force already has aircraft —  from the purpose-built A-10 to fighters like the F-16 — that are able to perform the close-air support mission.

James also pushed back on industry claims that the Air Force plans to expand use of its new T-X trainer for close-air support missions.

Lt. Gen. Mike Holmes, the deputy chief of staff for strategic plans and requirements, said earlier this year that the service was pushing T-X competitors to include additional power, cooling and payload capacity in the hopes of creating more flexible trainers that could possibly be adapted for the CAS mission. However, James said that she was not aware of any proposal to use the trainers as an A-10 replacement and that no decision had been made.

In recent months, the service's top uniformed leaders, such as Air Force Chief of Staff Gen. David Goldfein and his predecessor Mark Welsh, have been bullish on a potential A-X aircraft. At the same time, they acknowledge that it would be difficult to buy a new CAS platform and still have money left for all of the service's other acquisition priorities, including the F-35, KC-46 tanker, B-21 bomber and an intercontinental ballistic missile replacement.

Extending the life of the A-10 is one of the options under consideration, Air Combat Command head Lt. Gen. Herbert "Hawk" Carlisle said July 7. However, given the age of the 1970s-era aircraft and the cost of making improvements to it, buying a new aircraft is currently the more appealing possibility.

"I can't say we've ruled that out," he told reporters at the Royal International Air Tattoo in England. "But I can say right now for us, an A-X looks more attractive than trying to keep the A-10 for infinitely longer just because of the service life extension programs, engines, avionics, everything that you'd have to do."

Twitter: @ValerieInsinna