Venezuelan President Hugo Chavez has narrowly lost a referendum on controversial constitutional changes.
The president said his battle for "socialism" would go on
Voters rejected the reforms, which included allowing a president to stand indefinitely for re-election, by 51% of the vote to 49%, officials said.
Mr Chavez accepted the result and urged his followers to remain calm.
Mr Chavez said his reform agenda would go on but correspondents say the result will put a brake on his self-styled "socialist revolution".
Celebrations began almost immediately in the capital, Caracas, among activists who had opposed the president's raft of proposals, which included ending limits on presidential terms, halting the central bank's autonomy and cutting the working week.
"Venezuela won today, democracy won today, and I am sure that this victory for the Venezuelan people will have a very important impact in the rest of Latin America," Leopoldo Lopez, opposition mayor of the Chacao of Caracas, municipality, told the BBC.
'Don't feel sad'
The BBC's James Ingham in Caracas says Mr Chavez had expected a big win and will be very disappointed.
However, the president swiftly conceded and urged the opposition to show restraint.
"To those who voted against my proposal, I thank them and congratulate them," he said. "I ask all of you to go home, know how to handle your victory."
He insisted that he would "continue in the battle to build socialism".
"Don't feel sad," he told his supporters.
"For now, we couldn't do it," he said, repeating words he spoke after his failed coup attempt in February 1992.
But he said he would continue to push his reform plans.
"I will not withdraw even one comma of this proposal, this proposal is still alive," he said.
Our correspondent says that some of Mr Chavez's loyal supporters have gone against him on this occasion.
Though some of them may still support him, he says, they think he has gone a little too far in a country which has a history of dictatorships.
BBC Americas reporter Julian Miglierini says many analysts are pointing to the abstention rate of 44%.
Indefinite re-election of president, term increased from 6 to 7 years
Central Bank autonomy ended
Structure of country's administrative districts reorganised
Maximum working day cut from 8 hours to 6
Voting age lowered from 18 to 16
Social security benefits extended to workers in informal sector
He says the bulk of those who abstained are thought to be Chavez supporters who chose not to endorse the reforms, while voters backing the opposition turned out in droves.
The result marks the president's first electoral reverse since he won power in an election in 1998.
Since then he has set about introducing sweeping changes in the country's laws aimed at redistributing Venezuela's oil wealth to poorer farmers in rural areas.
Just a year ago, he was re-elected with 63% of the vote.
But analysts say the defeat should cause him to rethink the pace and scope of his reforms.
Having lost the vote, the current rules state that he will have to stand down in 2013.
The White House welcomed the result.
"It looks like the people spoke their minds, and they voted against the reforms that Hugo Chavez had recommended and I think that bodes well for the country's future and freedom and liberty," spokeswoman Dana Perino said.