bank@ (Adds analyst comment, economic context, updates peso and stock market levels)
BUENOS AIRES, May 17 (Reuters) - Argentina's peso weakened slightly to 24.30 per U.S. dollar on Thursday and the central bank offered to intervene in the spot market, traders said, a day after President Mauricio Macri promised to quicken the pace of deficit reduction.
The central bank offered to sell $5 billion of its reserves at 25 pesos per greenback. Chief monetary policymaker Federico Sturzenegger drew the line at that level on Wednesday when he said a peso at 25 per dollar would be "out of scale."
The Merval stock index was up 0.7 percent, bringing its gains over the last seven sessions to more than 20 percent.
Macri said late on Wednesday that recent turbulence in the foreign exchange market, which had pushed Argentina's currency down to record lows, was over. He vowed to double down on his effort to reduce Argentina's fiscal deficit.
It was the latest move by Macri, elected in 2015 on a pro-investment platform, to regain market confidence after weeks of volatility sparked by a new tax on foreign investors, and the country's weak economic fundamentals, including 12 month inflation running at 25.5 percent as of the end of April.
Last week, he requested a "high access stand-by arrangement" from the International Monetary Fund. The deal may include tough limits on government spending after Macri's gradualist approach to fiscal reform failed to halt the peso's slide. He vowed to accelerate the pace of fiscal belt tightening.
"The world decided that the speed with which we had committed to reduce the fiscal deficit was not enough in terms of guaranteeing that we are going to do it with the seriousness and depth that is needed. That's why we have to accelerate," Macri told reporters.
Earlier this month, his administration lowered its 2018 fiscal deficit goal to 2.7 percent of gross domestic product from 3.2 percent previously.
"The main points ahead are the details of the arrangement with the IMF," said Gabriel Zelpo, chief economist at local consultancy Elypsis, who estimates the government needs about $33 billion from the multi-lateral lender over the coming year.
"We estimate that a good arrangement with the IMF should be of about that size," Zelpo said. "Investors are waiting to see how intense the fiscal reduction requirement will be and, most important, what the size of the credit package will be."
Those details will be "developed in the coming days," an IMF official told reporters in Washington.
Resorting to the IMF is politically sensitive for Macri, who is expected to run for re-election next year. Many Argentines believe it was IMF policies that set the stage for the country's 2001/02 economic meltdown, which tossed millions of middle class Argentines into poverty.
Protests against Macri's deficit-cutting program and the upcoming IMF deal are being held daily, blocking streets in capital city Buenos Aires.
Wednesday was the first trading session since May 9 that the bank did not sell reserves to prop up the peso. The currency has weakened about 16 percent this month. (Additional reporting by Walter Bianchi; Editing by Jonathan Oatis, Chizu Nomiyama and Susan Thomas)