(Recasts with lower house speaker delaying vote)
BRASILIA, Dec 14 (Reuters) - The lower house of Brazil's Congress will delay a vote on a bill trimming social security benefits until Feb. 19, Speaker Rodrigo Maia said on Thursday, pushing a decision on the cornerstone of President Michel Temer's fiscal reforms into an election year.
Temer had said he hoped for a vote by Tuesday, but he has struggled to rally lawmaker support for the unpopular pension cuts, which many investors consider essential to reining in Brazil's surging public debt.
Brazil's currency, the real, fell 0.8 percent on Wednesday, flirting with a seven-month low against the U.S. dollar.
Investors fear that failure to streamline social security could weaken Brazil's recovery from a deep economic downturn, forcing the central bank to raise interest rates from an all-time low and potentially triggering new sovereign rating downgrades in 2018.
"This raises the possibility that the reform will not be approved next year, given political uncertainty surrounding the presidential elections," said Samar Maziad, a senior analyst at Moody's Investors Service, calling the delay "credit negative."
The bill would require Brazilians to work longer before retiring and cut generous pensions for public-sector employees.
Lawmakers may be more reluctant to back the austerity measure as elections approach in October, but Maia suggested they would rise to the challenge.
"Even though 2018 is an election year, the fiscal crisis is so big that it will be possible to get pension reform approved," he said.
Temer's last-ditch effort to sell the bill this year was cut short on Wednesday, when he had to fly to Sao Paulo for surgery to treat a narrowing of his urethra.
His office said the surgery was successful and that he would remain in the hospital until Friday to recover.
The surgery forced Temer to cancel meetings scheduled to muster votes for the bill, including the swearing in of a new political affairs minister.
It became clear this week that Temer did not have the three-fifths super majority, or 308 votes, needed to pass the bill in the lower house of Congress.
While ministers were still working to gather more votes, the government's chief whip in the Senate stunned the administration on Wednesday by saying the vote had to be put off to February.
Finance Minister Henrique Meirelles said he hoped pension reform can be enacted by March.
His ministry estimated that approving pension reform would boost its 2018 growth forecast by 0.30 percentage points. (Reporting by Maria Carolina Marcello and Anthony Boadle; Editing by Lisa Von Ahn and Richard Chang)