WASHINGTON — The US Air Force is deliberating if and how to replace its close-air support workhorse, the A-10, and may have a better picture of their path forward later this year, the service's top civilian said Wednesday.

During an interview with Defense News, Air Force Secretary Deborah Lee James said she and other top service leaders — such as Chief of Staff Gen. David Goldfein — will be briefed on various options for replacing or augmenting the A-10 Warthog this fall, as the service begins to build its next five-year budget plan.

"Any of these types of possibilities would likely come up in the fall to me and the chief during this planning choices forum. And that's when we would discuss and we could make some recommendations," which could then flow into the budget cycle, she said.

Air Force officials recently briefed a group of analysts and aerospace experts on a proposed plan that would involve buying two close-air support (CAS) aircraft. In the near term, the service would procure an existing light-attack aircraft to augment the A-10 during CAS missions in permissive environments. This OA-X would likely be an existing aircraft with a low flight-hour cost, such as the Beechcraft AT-6 or Embraer A-29 Super Tucano. Further down the road, the Air Force would purchase an A-X2 — which could be an existing or new design — that would replace the A-10. That jet would operate in slightly more sophisticated, medium-threat environments.

However, James stressed that other options, such as re-winging the A-10 or buying a single aircraft to replace the Warthog, were still on the table.

Although not all Air Force leaders have been briefed on the various proposals, some top officials — including James — have questioned the viability of the dual-aircraft plan. On Wednesday, she reiterated that if the Air Force were to add a CAS aircraft to its already crowded procurement budget, another program would have to take a hit in funding.

"Everything has a price tag," she said. "If something goes in, something else has to fall out."

Although the exact cost of the program would depend on the service's requirements and planned procurement quantities, a new-start program could entail spending "tens of billions" of dollars, Todd Harrison, a defense budget analyst at the Center of Strategic and International Studies, said during an event Tuesday.

The Air Force will consider all available funding sources, including the Overseas Contingency Operations account used to pay for wartime expenses, James said, but using the OCO account might not be the best choice for paying for certain options. Aircraft procurement and development, for instance, are multi-year endeavors that need a steady, reliable stream of funding, while OCO is primarily used to pay for one-time or very short-term outlays.

Air Combat Command chief Gen. Herbert "Hawk" Carlisle has said he's unsure if buying a low-end CAS platform is the best use of taxpayer dollars. In a Tuesday briefing, he referenced the Air Force's modernization bow wave, a period in the early 2020s during which the service will bear the cost of a plethora of expensive platforms, including the F-35, B21 bomber, KC-46 tanker and various nuclear and space systems.

"If you look at the things within the combat Air Force portfolio that I'm responsible for in modernization and taking care of those systems, I don't know where the money would come from," he said. "And if we got extra money, in my opinion, there's other things that I would do first to increase our combat capability before we go to that platform."

He also raised concerns about whether a low-end CAS platform would be quickly rendered obsolete as adversaries become increasingly able to access surface-to-air missiles and other munitions capable of taking down less-advanced aircraft.

"Given the evolving threat environment, I sometimes wonder what permissive in the future is going to look like and if there's going to be any such thing, with the proliferation of potential adversaries out there," he said. "The idea of a low-end CAS platform, I'm working my way through whether that's a viable plan or not given what I think the threat is going to continue to evolve to, to include terrorists and their ability to get their hands on, potentially, weapons from a variety of sources."

James said it's "prudent" for the Air Force to explore its options, given congressional interest and a changing threat environment that has made close-air support a more urgently needed capability.

"Having additional capacity, if we're able to afford that capacity, is not a bad thing," she said. "Additional capacity in view of changed world conditions could be helpful."

Twitter: @ValerieInsinna