Crossbench senators are being urged to hold firm against controversial plans to drug test welfare recipients, which will almost certainly be postponed after crucial last-minute negotiations.
Social Services Minister Christian Porter is locked in talks over a broad suite of welfare measures bound for the upper house on Tuesday.
Among them are plans to drug test 5000 Newstart and Youth Allowance recipients across three trial sites in NSW, Queensland and Western Australia from January.
Mr Porter has indicated he is willing to put off the trials so other changes are not delayed, but intends to pursue negotiations right up until the legislation lands in the Senate.
"What I will be saying to crossbench senators is that everything we are doing to move people from welfare to work is working," he told AAP.
"The welfare reform bill before the Senate is the next critical step in reforming the welfare system to get even more people to break the cycle of welfare dependency."
Under the Turnbull government's plan, anyone who tests positive would be shunted onto cashless welfare cards, while those who fail more than once would be referred to medical professionals for treatment.
Rebekha Sharkie from the Nick Xenophon Team has previously spoken out against the trials but is expected to meet with the minister.
Australian Medical Association president Michael Gannon is urging the crossbench to block the trials, which Labor and the Greens oppose.
"It might have appeal, this idea, but it doesn't work," Dr Gannon told AAP.
"We don't think this is a fair measure and we think that it has the potential to further marginalise an already vulnerable group of Australians."
If the government were to remove the drug testing trials, the resulting separate piece of legislation would probably have to wait until parliament returns in February.
The remaining legislation would introduce a demerit point system for people who persistently dodge job-seeking obligations, tighten exemptions around drug and alcohol dependence and fold seven different existing payments into one.
Cassandra Goldie, from the Australian Council of Social Service, said the bill contained disturbing cuts to bereavement payments and scrapped protections for people with extenuating circumstances to claim income support.
"Drug testing may be off the table, which is very welcome, but the bill has a raft of other social security cuts and changes that will make life tougher for people already struggling with poverty in Australia," Dr Goldie said.