The Air Force is taking a key step toward developing a dedicated close-air support plane to replace the A-10 "Warthog," a top general said Thursday.

"My requirements guys are in the process of building a draft-requirements document for a follow-on CAS airplane," Lt. Gen. Mike Holmes, the deputy chief of staff for strategic plans and requirements, said. "It's interesting work that at some point we'll be able to talk [about] with you a little bit more."

Speaking to reporters following a breakfast hosted by the Air Force Association, Holmes said a list of possible requirements for the aircraft will soon be given to Air Force Chief of Staff Gen. Mark Welsh.

"I have seen a draft of it, it's out for coordination. It'll go to the chief sometime this spring, and then we'll fold that into the larger study we're doing on the future of the combat air forces."

The possible new aircraft is part of Holmes' planning for the future of the Air Force over the next 15 to 20 years.

The Air Force is drawing up the list of requirements for close-air support, and would then analyze what would best meet the service's needs: building a new aircraft, using existing aircraft, or extending the life of the A-10, Holmes said.

"The question is, exactly where is the sweet spot … between what's available now and what would the optimum CAS replacement be," he said. "We're working along that continuum to see exactly where the requirement is that you can afford in the numbers we need to be able to do the mission."

The general cautioned that a lot will depend on Congress as well, and whether another round of mandatory budget cuts under sequestration occurs in fiscal years 2018-19  18 and 19.

"We are looking at what it could take to be able to do that, but the commitment to go forward to do that is a long ways off in the planning process," Holmes said.

He added that top brass would also need to compare the affordability of building a new airplane versus "what we're paying to keep flying the A-10 and maintaining it" currently.

Meanwhile, several existing and development aircraft could meet the CAS mission, Holmes said, pointing to light fighters like the A-29 Super Tucano attack plane, the AT-6 trainer aircraft and Textron AirLand's Scorpion.

The Air Force will also look at potentially re-purposing the T-X advanced trainer airframe for the CAS mission down the road, Holmes said. Although officials do not expect to add new requirements to the plane, which is in the early competition stages, the service will incentivize bidders to include excess power, cooling and space in their proposals to allow for flexibility in future, he said.

But for now the service is focused on developing and procuring 350 T-X jets to replace the service's aging T-38 trainer fleet, Holmes stressed.

"We're really careful with the T-X requirement because if we add requirements to T-X now, then it could become unaffordable and we can't replace the trainer role that we need it to replace," Holmes said. "There is an option down the road that you might take the airframe that's designed for T-X and use it for some other use, we have some money in our budget that will let us do the studies to do that."

The Air Force has long stated that the multirole F-35 joint strike fighter will perform the CAS role after the A-10 retires, but the new push for an A-10 replacement an A-X seems to indicate the service is bowing to pressure from the public and Congress to maintain a single-role close-air support aircraft to protect soldiers on the ground.

The Air Force's latest plan, reflected in the fiscal 2017 budget request, is to retire the A-10 by fiscal 2022. But in the out-years, the F-35 can only partially fill the capability gap left by the A-10, officials have said

"I would never look at you and tell you, 'Hey, the replacement, one-for-one, for the A-10 is the F-35,' " said Air Force Vice Chief of Staff Gen. David Goldfein last month.

Still, as the Air Force looks to define the future of CAS, officials and analysts say the service must keep in mind that the mission has changed drastically since the A-10 was developed in the 1970s. Today, the Air Force can perform CAS with bombers and fighter jets like the F-15, F-35 and B-1. In addition, UAVs like the MQ-1 Predator and MQ-9 Reaper can also supplement the mission while keeping pilots out of danger.

Lara Seligman with Defense News contributed to this report.