Vulnerable Australians are trying to balance their need for government-funding services while supporting moves to keep the NDIS financially stable to ensure future access.

The government has put an eight per cent cap on the scheme's growth each year by mid-2026 with the NDIS on track to cost the public purse more than $50 billion by 2025/26, overtaking annual spending on Medicare.

The chief executive of one of Australia's largest disability service providers says the cap is necessary to maintain faith with the taxpayer.

"An eight per cent growth cap guarantees the scheme's future both for people with a disability and for the taxpayer who knows the costs are being reined in," ARUMA's Martin Laverty told AAP on Monday.

Dr Laverty said the sustainability of the scheme was under pressure with the 410,000 participants predicted when the scheme started having grown to 600,000.

He said it would be challenging to keep the costs within the cap, but it could be achieved through an honest conversation about who the NDIS was for, what services it covers, how costs are shared and cutting red tape.

"Every person in the NDIS has a red tape headache in accessing the support they need," he said.

"Getting rid of the red tape not only saves costs but makes life easier for people with disability."

Chair of the National Disability Insurance Agency Kurt Fearnley vowed to keep vulnerable people at the heart of the disability program despite funding pressures on the scheme.

"So many people with disabilities, they hear the word 'cap' and shudder. I shudder," he told ABC radio.

"We are a demand-driven scheme. The target is a bit of a challenge."

Disability care provider Life Without Barriers said while there was a need for reform, it needed to be done in the best interests of vulnerable Australians.

"We know how important continuity of services is for the people we support and to be able to achieve that, we need an NDIS that is both sustainable and meeting the needs of people with disability," chief executive Claire Robs said.

Ms Robs said service providers had an important role to play in working with the government and agency to get the balance right and ensuring there was enough information for participants.

"For the scheme to be truly about and for people with disability, then we have a responsibility to ensure people with disability understand what reforms to the NDIS may mean for them now and also the benefits in the long term."

The scheme was discussed by state and territory leaders at national cabinet as governments work to make the scheme more financially sustainable.

The Commonwealth is set to fund the majority of the scheme instead of it being a 50-50 split with the states.

South Australian Premier Peter Malinauskas said the states didn't have the capacity to fund half of the enormous costs of the scheme as they battled blowout spending on health.