BRASILIA (Reuters) - Brazil’s government has no clear timeline for winning approval in Congress for pension reform, the cornerstone of its plan to control a gaping budget deficit, as it strives to secure the necessary votes, officials said on Tuesday.

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The unpopular bill, which would force Brazilians to work years longer before retirement, cleared a congressional committee last week by 23 votes to 14.

It was meant to be put to the vote in the lower house this week but that now is not expected to happen for two or three weeks.

Investors are worried the bill will undergo further dilution with concessions by President Michel Temer’s government to win over unconvinced lawmakers who are worried angry voters will punish them in the coming election year.

“We are working to widen the margin of votes for the pension reform,” Trade and Industry Minister Marcos Pereira told reporters, declining to say when the bill would be voted.

The constitutional amendment, which could reduce Brazil’s current budget deficit by almost half, needs to be passed twice by three-fifths of the members of both chambers.

In the lower house that requires 308 votes. According to ARKO Advice, a political analysis firm in Brasilia, the government has secured 313 votes, a margin too narrow to risk a rapid vote.

Temer’s point man for relations with Congress, Antonio Imbassahy, told reporters after a strategy meeting with the president on Sunday that the government is sure the pension reform will pass, but the date for putting the bill to the vote will depend on mustering support from its coalition in Congress.

The head of the ruling PMDB party and government leader in Congress, Senator Romero Jucá, said the pension reform bill will sail through the Senate without interference.

The crucial battle will be in the lower chamber, where lawmakers are playing for time to obtain more concessions from the government. That could further water down the measure.

“Congressmen are seeking more concessions and the government is negotiating, and it will get the votes it needs,” said Lucas de Aragão, a political scientist and partner at ARKO.

He said Finance Minister Henrique Meirelles would meet with the farm lobby in Congress to secure their backing in return for help with a debt of 10 billion reais ($3.1 billion) owed by the agribusiness sector to a pension fund for rural workers.

Meirelles has said the bill as it stands has lost 25 percent of planned savings - down to 600 billion reais over 10 years - and more concessions are out of the question if the bill is to be effective in reducing the deficit and helping to bring down interest rates.

Brazil lost its investment grade credit rating two years ago and needs to restore confidence in its government accounts to stir investment and shake off a two-year recession.

Fitch Ratings, which rates Brazil BB or two notches below investment grade, said on Tuesday it would await further clarity over the approval of Temer’s reform agenda before reviewing the country’s sovereign rating.