This story was originally published April 7, 2016, at 12:22 p.m. EST.

WASHINGTON — The Air Force is moving forward with a key step in 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 with you a little bit more."

Defining the requirement is the first concrete step toward potentially developing a replacement A-10 for the close-air support mission, often dubbed A-X. The Air Force has been studying the idea of a procuring single-role A-X for at least a year now, hosting a joint-service summit in March, 2015, to work out options for the close-air support, or CAS, mission.

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

"That CAS replacement airplane, I have seen a draft of it, it's out for coordination. It'll go to the Chief sometime this spring and let the Chief shape it, he's our chief requirements officer also in the Air Force, and then we'll fold that into the larger study we're doing on the future of the combat air forces," he said.

Once the requirement is firm, the next step will be deciding the most cost-effective way to meet that need, Holmes said. The Air Force will weigh the capability and affordability of three alternatives: building a new A-X, using existing aircraft to meet the CAS mission, or extending the life of the A-10, Holmes said.

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

For an A-X, the general cautioned that a lot will depend on Congress and whether another round of mandatory budget cuts under sequestration occurs in fiscal years 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.

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, though adding: "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-X seems to indicate the service is bowing to pressure from the public and Congress to maintain a single-role 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. UAVs like the MQ-1 Predator and MQ-9 Reaper can also supplement the mission while keeping pilots out of danger.

Phillip Swarts with Air Force Times contributed to this report.

More In Air Warfare