CANBERRA, Sept 13 - Nick Xenophon says his team of three senators cannot support the measures as they stand while independent Derryn Hinch predicts they won't pass without changes.
Nevertheless, ever-buoyant Education Minister Simon Birmingham is hopeful of reaching a deal soon on his higher education package.
It includes cutting university funding in 2018 and 2019, increasing student fees, lowering the repayment threshold for HECS-HELP student loans and tying a portion of funding to performance measures.
The higher education sector opposes the package, which it says will cut $2.8 billion over the next four years and leave students paying more for less.
Labor and the Greens have followed suit, leaving the government relying on crossbench votes once the legislation reaches the Senate.
The NXT education spokeswoman Rebekha Sharkie is likely to outline her party's specific concerns during debate on the legislation in the lower house on Wednesday.
Senator Xenophon believes the legislation needs to grapple with the differences in demand and supply of skills and not continue the siloing of university and vocational education.
Senator Hinch has "some major worries" about aspects of the package, including the proposal to make graduates start repaying loans when their income hits $42,000 - down from nearly $56,000 at the moment.
He's hoping for a compromise level of $50,000.
The tricky task for the government will be to win them over while keeping supporters onside - such as Australian Conservatives senator Cory Bernardi, who warned he was looking to save taxpayer money.
While Senator Hinch wants a higher loan repayment threshold, Senator Bernardi believes the government could go even lower, citing policy in the UK and New Zealand.
"People need to be held accountable that they've borrowed money from the taxpayers," he said.
Senator Birmingham wasn't put off by the tough task.
"The Senate's always a balancing act," he told reporters.
"But we've pragmatically dealt with them successfully as a government since last year's election and I am confident we will be able to continue to do so and hopefully will get a result in relation to higher education."