(Adds President Temer's appeal to Congress to approve bill, lower house speaker wants vote in February)
BRASILIA, Feb 5 (Reuters) - President Michel Temer appealed to Congress on Monday to approve his pension reform proposal to bring Brazil's budget deficit under control, but a cabinet minister said his government still lacks some 40 votes to pass the unpopular bill.
Congressional leaders said that the plan to overhaul the costly social security system would never get through if it was not voted on this month before lawmakers begin to focus on the October general election.
"We have made adjustments to the bill to address legitimate concerns and create softer rules of transition. Now the time has come to take a decision," Temer said in a message to Congress at the start of the legislative year.
His minister in charge of political affairs, Carlos Marun, however, told reporters the government was 40 votes short of the two-thirds super majority of 308 needed for approval.
Marun said he was confident that the bill would pass this month because there are between 80 and 100 Congressmen who have not yet made up their minds.
The postponement of a vote in December has raised doubts about Temer's ability to rein in a bulging budget deficit that cost Brazil its investment grade credit rating in late 2015.
Economists said Brazil's deficit is unsustainable and mainly driven up by pensions. In GDP terms it has more than doubled between 2014 and 2017. Official figures released last month showed that the social security deficit grew by 18.7% in real terms in 2017, to a record 268.8 billion reais ($82.49 billion).
"The pension vote must be in February. If we delay further, we will never pass it," lower house Speaker Rodrigo Maia said at a news conference. "Nobody will be able to govern Brazil next year if spending reforms are not made."
Lawmakers returned from their recess on Monday to start debating the bill, which the government plans to put to the vote after next week's Carnival holiday.
Government whips were negotiating with lawmakers for further concessions to make the bill more palatable to the lower chamber. But they said important provisions such as the introduction of a minimum age of retirement were not on the table.
($1 = 3.2627 reais) (Reporting by Maria Carolina Marcello, Marcela Ayres, Ricardo Brito and Leonardo Goy; Writing by Anthony Boadle; editing by Grant McCool)