The outcome of Venezuela's referendum on constitutional reforms is still too close to call, government officials said late Sunday. If the vote passes, President Hugo Chavez could seek re-election indefinitely.

"The result of the referendum is close," vice-president Jorge Rodriguez told reporters from Chavez's campaign headquarters. "We will respect the result, whatever it is -- even it's by one single vote."

Some officials claimed exit polls showed Chavez leading by a narrow margin, while opposition members claimed the socialist leader was losing.

If Chavez wins, the victory would allow him to run for office as many times as he wants, strengthening his grip on the oil-rich country of 26 million people.

Under current laws, Chavez must step down as president in 2012 -- the end of his third term in office.

Diego Navarro, a member of the international team of observers in the country for the referendum, told the press that voting proceeded efficiently.

"Everything is moving quickly and well, and I noticed that the voting process for a person has been carried out within five minutes," he said before polls closed.

Other reforms among the more than 30 proposed include giving Chavez control over the central bank and allowing him to personally choose provincial and municipal leaders.

If passed, they would also allow his government to detain citizens without charges during a state of emergency and extend presidential terms from six to seven years.

Some pollsters say the outcome of the referendum is too close to call, which could fuel violent street clashes.

Chavez, 53, has warned the U.S. to not interfere with the election and has threatened to block oil exports to the country -- the primary buyer of Venezuelan oil.

Chavez, first elected president in 1998, says the constitutional changes are vital to making the country a socialist state.

He has said anyone who votes against the reforms are pawns of U.S. President George Bush.

Opponents -- including Roman Catholic leaders, press freedom groups and human rights groups -- say the reforms would be a threat to basic human rights.

In the days leading up to the vote, Chavez said he would remain in power until 2050 if he was healthy. He would be 95 years old.

With files from The Associated Press