Venezuelan President Hugo Chavez has admitted defeat in a referendum on constitutional changes that would have granted him greater power, including the ability to run for re-election indefinitely.

The country's electoral authority Monday said 51 percent of voters said "no" to the proposed changes, while 49 percent supported them.

The vote is seen as a huge defeat for Mr. Chavez. He had said before the vote he was prepared to stay in power until 2050, when he would be 95 years old.

Under the current constitution, he will not be able to run for re-election when his term expires in 2013.

The changes would have granted the government sweeping new powers in case the president declares a national emergency. They also would reduce the workday in Venezuela from eight hours to six hours, and extend social benefits to more workers.

Thousands of people staged demonstrations in Caracas last week, both for and against Mr. Chavez's proposals.

After several public-opinion surveys reported public sentiment was tipping away from the president, Mr. Chavez raised the possibility last week that the United States could interfere with the election. Officials in Washington repudiated his comments, but Mr. Chavez followed up by threatening to cut off oil shipments to the United States if he saw evidence of any interference.

A prominent member of the U.S. Senate, Carl Levin, also rejected Mr. Chavez's allegations. The American lawmaker said Sunday that the United States is not seeking to destabilize Venezuela.

In response to warnings by opposition parties, human-rights groups and Venezuela's Roman Catholic leaders that passage of the referendum would amount to an unprecedented concentration of power in the president's hands, Mr. Chavez has argued that it is necessary to revise the constitution to strengthen the people's voice in government.

Some information for this report provided by AP, AFP and Reuters.