Ajax is a group of armoured vehicles with reconnaissance and recovery capabilities and all the vehicles are expected to be delivered by 2029.
If there are no more orders then the production lines at Merthyr will be empty and the hundreds employed on the project will be out of work.
But Defence Minister Luke Pollard told BBC Wales he was “confident” there would be enough interest from UK Nato allies in what he called the “incredible” and “lethal” armoured vehicles to secure the future of the plant.
“It has had problems in the past,” he said.
“It was right that trials were paused to look at those problems, but it was also right that the company got on top of them, working with the army, working with the Ministry of Defence and General Dynamics to fix them.”
“We now have an incredible, capable, next generation capability, that’s safe for the men and women of our forces to use, but importantly, is lethal against our adversaries if used on the battlefield”.
“So it’s a really key part of our next generation British Army capabilities. But as a minister, I would not be putting it into service if I had any doubts about its safety.”
General Dynamics has two sites in south Wales, with Merthyr Tydfil’s armoured vehicles using communications equipment developed at Oakdale in Caerphilly county.
Apprentice Charlie Penfold said he was really proud to work on the project.
“It’s incredibly prestigious when you work with the military and if you speak to friends or family and you say ‘I build armoured vehicles’ – there’s always a bit of a wow factor.
“I get to come here every day and look at these amazing vehicles.”