After breezing through past elections, Venezuelan President Hugo Chavez entered the last week of campaigning Sunday against a rival who has gained ground in opinion polls.

The leftist leader, in power for almost 14 years, is vying for a fourth term in office that would extend his presidency by another six years, but opposition candidate Henrique Capriles hopes to pull a major upset on October 7.

The telegenic former governor of Miranda state has compared himself to David fighting Goliath. And he hopes he can emulate the Bible story of the boy who felled the mighty giant before becoming king of Israel.

Chavez, who used the country's oil wealth to reduce poverty, brushed aside his last rival in 2006 by taking almost 63 percent of the vote.

The latest opinion poll gives the 58-year-old incumbent a 10-point advantage over Capriles, but the 40-year-old challenger has cut the lead by half in just four months.

Chavez was favored by 49.4 per cent of voters compared to 39 per cent for Capriles in the poll released this week by Datanalisis. A significant number of voters, 11.6 per cent, remain undecided.

Other polls give Chavez a bigger leader while some found a statistical tie.

"All the big polling firms show a narrowing gap and a significant increase in voter intentions in favor of the opposition leader," said Datanalisis president Luis Vicente Leon.

But Chavez, who declared victory over cancer in July, has voiced confidence that he would win re-election and use the next term to make his socialist revolution permanent.

"They know that they are losing, that the gap is irreversible," Chavez told thousands of supporters this week at a rally in the western state of Falcon, where people danced to the election song 'Chavez, heart of the people'.

True to his provocative style, Chavez has derided his rival as a 'loser' and a 'political illiterate' who would bring chaos to Venezuela.

Chavez said he believed he had beaten cancer and would be strong enough to rule for another six years if he won re-election on October 7.

"I think so, I feel great," he told AFP when asked if he had fully recovered from his illness.

"If I didn't feel strong enough, I wouldn't be here. We're even going to work at a faster pace," he added.

With Chavez dominating the public airwaves, Capriles has taken a page out of the president's own playbook by taking his campaign directly to the people, going door to door to meet with ordinary Venezuelans.

Capriles, who campaigns with a baseball cap in Venezuela's colors, has sought to bring a fresh face to the opposition, which has been associated with an old system of parties that shared power for 40 years until Chavez's rise.

"We must defeat Goliath, and each one of you is David. I am David, but each one of you is David too," he told a rally this week that played his own campaign song, "There is a path."

Capriles has seized on the country's high murder rate -- 50 homicides per 100,000 inhabitants in 2011 -- to criticise the president's handling of the country's crime wave.

While the government accuses him of conducting a US-style 'marketing' campaign, Capriles promises to improve the lot of Venezuelans by maintaining and improving Chavez's socialist programs.

Despite the opposition candidate's rise in opinion polls, political analyst Farith Fraija noted that the president continues to count on 'hardcore Chavez voters who give him a comfortable edge of more than 10 points'.

Capriles, for his part, has to rely on the 'unpredictable' undecided voters to have any hope of winning, Fraija said.