Investors widely see the unpopular bill as crucial to regaining an investment grade rating, meeting budget laws and avoiding a fiscal crisis.
But lawmakers have shown strong resistance to the constitutional amendment, raising the threat that a lower house vote is delayed to early 2018.
The government agreed with lawmakers to schedule a Dec. 18 vote on the bill, the week before Christmas recess. But President Michel Temer acknowledged the vote could happen only next year, dialing back on last week's strict rhetoric.
An early 2018 vote would edge dangerously close to presidential and parliamentary elections, making approval more unlikely.
The Brazilian real firmed 0.1 percent, while the benchmark Bovespa stock index rose 0.8 percent.
Trading in most Latin American markets was muted as investors avoided making big bets ahead of central bank meetings across the region.
Central banks in Mexico, Colombia, Chile and Peru will meet throughout the week to set benchmark interest rates.
Also helping to foster caution, the Federal Reserve is scheduled to release its monetary policy statement on Wednesday.
The Fed is widely expected to raise interest rates, and is seen possibly tightening two or three times in 2018. But still-sluggish inflation and wage growth has clouded next year's policy outlook.