(Recasts to add background, forecast for overall budget data)
By Luciana Otoni
BRASILIA, March 27 (Reuters) - Brazil's central government budget slipped into deficit in February, underscoring President Dilma Rousseff's struggle to shore up public finances and regain credibility with investors.
Brazil's central government, which includes results from federal ministries, the central bank and social security, posted a primary budget deficit of 3.078 billion reais ($1.356 billion) in February, the Treasury said on Thursday.
February's gap comes after a lower-than-expected surplus of 12.954 billion reais in January.
Brazil's public finances have deteriorated over the past few years, leading Standard & Poor's to downgrade the country's debt rating closer to junk status on Monday.
Brazil's government pledged to save 99 billion reais this year in primary surplus, or 1.9 percent of the country's GDP. But economists in a Reuters poll last month said that target is probably out of reach.
The central bank on Friday is scheduled to release the country's consolidated fiscal results, which adds states and municipalities and is regarded as the benchmark for Brazil's fiscal performance.
The median expectation of 16 economists in a Reuters poll carried out earlier in the week is for a deficit of 500 million reais in Brazil's consolidated budget.
$1 = 2.2700 Brazilian reais Reporting by Luciana Otoni; Writing by Silvio Cascione; Editing by James Dalgleish and Stephen Powell