Finance Minister Mathias Cormann still intends to have a Senate vote on the remainder of the Turnbull government's 10-year business plan this week before parliament rises for the long winter break.
However, so far the government has only secured the backing of four of the eight crossbench senators needed to pass the legislation that would cut the corporate tax rate to 25 per cent from 30 per cent for all firms.
Senator Cormann, who is the government's chief negotiator in the upper house, says the government remains committed to securing its passage this week.
"We are not in charge of our own destiny in the Senate but that is certainly our intention," he told Sky News.
Senator Corman also ruled out a compromise deal that would limit reductions to businesses with a turnover of up to $500 million, as backed by independent Derryn Hinch, because he would then lose the support of fellow crossbencher David Leyonhjelm.
The two Centre Alliance senators haven't budged in months in their opposition to the tax plan, neither has independent Tim Storer.
The government fell short two votes when it tried to get the tax plan passed just before Easter, but One Nation has since reneged on a previous deal to support the cuts.
Labor took the spotlight on the government's negotiations on Tuesday when leader Bill Shorten promised, if elected, to roll back already legislated tax cuts for businesses with turnovers between $10 million and $50 million.
It drew a sharp response from business groups.
"This announcement pulls the rug out from underneath many hard working small and medium and family businesses," Australian Chamber of Commerce and Industry chief executive James Pearson said.
Adding to the uncertainty, Labor is still considering what it will do about tax cuts already in place for businesses with turnovers between $2 million and $10 million.