* Economy minister due to outline details on Thursday
* Opposition prepares to block bill with eye on election
* Current budget would be extended if no deal reached
* Gov't has broad powers to expand, redirect spending (Updates after bill submitted)
By Magdalena Morales
BUENOS AIRES, Sept 15 (Reuters) - Argentina's government sent its 2011 budget to Congress on Wednesday without revealing details of the bill, which opposition lawmakers have vowed to block if it low-balls inflation.
Recent budgets have included conservative estimates of growth and revenue despite brisk economic expansion, letting the government spend "additional" income without congressional oversight. They have also underestimated inflation, the opposition says.
Congress rubber-stamped the budget from 2003 through 2009, but President Cristina Fernandez lost her congressional majority last year. Political jockeying ahead of an October 2011 presidential vote makes a stand-off even more likely.
"If the government budget is as deceitful as always, they won't have the votes (to pass it)," leftist opposition legislator Claudio Lozano told Reuters.
Economy Minister Amado Boudou is due to outline the main points of the bill in Congress on Thursday at 10 a.m. local time (1300 GMT).
Ruling-party lawmakers say they will not accept major changes to the bill and have raised the possibility of governing without a budget, which has happened in Latin America's No. 3 economy during political or economic crises.
If talks on the budget end in deadlock, by law the previous year's budget is extended automatically, which theoretically caps spending.
But ultimately, the government will be able to spend as it sees fit since it has so-called "superpowers" to redirect outlays without congressional approval and can issue an emergency decree to acknowledge more spending after the fact.
Fernandez is expected to issue such a decree later this year to formalize additional spending, not accounted for in the 2010 budget, which some analysts say could total as much as 60 billion pesos ($14.98 billion).
Opposition lawmakers have moved to repeal these superpowers, first passed in 2006, and also limit the scope of emergency decrees. But they have not yet been able to get these reforms passed by both houses of Congress.
"The proposal will include a significant underestimation of fiscal revenue so that, once again, the government can use the extra resources according to their political needs," Analytica consulting group said in a report this week.
"This will be crucial in an electoral year," the report added.
INFLATION
The main sticking point in the budget is inflation, which economists, opposition politicians and even some renegade state statisticians say has been systematically underreported since early 2007 for political gain and to reduce debt payments.
"Real" inflation is estimated at between double and triple the official rate, and opposition legislators running the ideological gamut have said they will not accept a budget that estimates single-digit inflation for 2011.
The 2010 budget forecast 6.1 percent average inflation for 2010, well below the 11.2 percent annual figure reported by the government through July and the 20-plus percent price rise forecast by private economists.
The government defends official inflation data and is expected to resist any efforts by the opposition to change the forecast for next year.
A deal could be reached if the government found allies willing to pass the bill with minor changes only. Or opposition lawmakers could try to push through their own version of the budget, but they would not have the two-thirds of votes needed to override a presidential veto. ($1 = 4.0075 Argentine pesos) (Additional reporting and writing by Hilary Burke; Editing by Nick Macfie)