Victoria's controversial assisted dying bill is set to be examined line-by-line in state parliament's upper house.
The Labor government, which introduced the bill, is hoping for a vote on Friday and the Legislative Council is expected to sit late into the night to debate the proposed scheme.
The bill is in a tight position, likely to pass only if tentative supporters can convince colleagues to make amendments.
"It will be a long debate," opponent David Davis told reporters on Monday.
"We will be working hard through the committee stage of the bill and many people have serious questions and legitimate points to put, and no doubt there will be amendments and it will be a long session."
Premier Daniel Andrews, who has been advocating for the laws, said on Sunday he would wait and see how the upper house debate unfolded.
"The time has come for us to put in place this system, with all the safeguards inherent in it," he said.
"Some people may need further comfort to make it even more conservative, we'll work with them in good faith."