* Correa admits win margin not as wide as forecast
* Says rivals and officials are manipulating count
* Reforms will give Correa power over judges, media
QUITO, May 12 (Reuters) - Vote counting in Ecuador showed President Rafael Correa heading for a referendum victory on Thursday after he accused electoral officials of delaying the tally in pro-government regions.
Correa, an ally of Venezuela's socialist President Hugo Chavez, had already declared victory after the vote on Saturday when polls and a quick count gave him a clear lead in the referendum on ten reforms that will give him more power over the judiciary and media in the South American OPEC nation.
But a sluggish official tally by the National Electoral Council initially indicated two key questions were facing rejection by voters and slim support for the others.
By Thursday, though, official counting showed all the reforms being endorsed.
"The 'Yes' vote has won in the 10 questions and it has won by a wide margin," Correa told reporters, while conceding that early polls showing an overwhelming victory had been wrong.
"We're happy because we're having a clear electoral victory, and the opposition is also happy because they expected a heavier defeat. We're all happy," he said.
With 67 percent of ballots counted, pro-Correa "Yes" votes on the questions ranged from 44 to 49 percent, while the "No" vote was between 41 and 44 percent.
Full coverage of the referendum [ID:nECUADOR]
Political risks in Ecuador [ID:nRISKEC]
Correa repeated his charges on Thursday that electoral officials had been in cahoots with the opposition.
"They counted the 'No' provinces first. That didn't happen by chance, that was deliberate," he said.
TESTING CORREA'S POPULARITY
By Thursday afternoon the council had finished counting votes from some 10 provinces that broadly rejected the measures, while the vote tallying from more densely-populated areas where Correa is popular was lagging.
Correa says the reforms are needed to get rid of corrupt and inefficient judges and let police fight crime better -- a huge concern in this Andean country of 14 million people.
Opposition leaders say the reforms are a power grab and fear he will appoint allies to top courts. They say a proposal to create a media watchdog threatens freedom of expression.
The referendum has widely been seen as a plebiscite on the president's popularity, since polls showed supporters planned to endorse the reforms -- even though they did not grasp them.
The charismatic 48-year-old economist has won a string of votes to increase executive power since taking power in 2007, prompting critics to cast him as the latest in Latin America's history of authoritarian leaders or "caudillos."
He has also boosted state spending on roads, schools and hospitals, making him very popular among the poor majority.
"Correa remains by far the most popular politician in Ecuador and ... the split vote reflects a desire to constrain Correa rather than to replace him," British-based newsletter LatinNews said on Thursday. (Additional reporting by Alexandra Valencia; Editing by Daniel Wallis)