GENEVA - Opposition politician Leopoldo Lopez said he was optimistic millions of Venezuelan voters would spark a democratic transition when they cast their ballots against incumbent Nicolas Maduro at presidential elections later in July.

The opposition has a substantial lead in opinion polls ahead of the July 28 vote, even after a court banned leader Maria Corina Machado from running over alleged fraud violations.

That forced her coalition to rally behind a new candidate, former diplomat Edmundo Gonzalez.

"It's impossible that the election would give Maduro victory without there being massive electoral fraud," Lopez, founder of the Voluntad Popular opposition party, told Reuters at the United Nations in Geneva.

"Of course, we know that Maduro is Maduro, that he is a dictator, but we are very optimistic that a transition to democracy will begin on July 29 in Venezuela."

Venezuela's Information Ministry did not immediately respond to a request for comment.

Maduro, a Socialist, seeks a third term in office. Western governments had dismissed his 2018 re-election as a sham.

The United States has urged Maduro's government to ensure that the elections are "competitive and inclusive".

With many Venezuelan voters angry about declining living standards, some analysts and opposition politicians say Maduro will struggle to overcome a lag in polling compared to Gonzalez.

There are doubts over whether the vote will be credible after Venezuela revoked an invitation to European Union election observers.

Lopez, who fled the country in 2020 and now lives in Spain, said it was unlikely the vote would be free and fair.

"There has been total censorship, the manipulation of the election registry," he said. "But the overwhelming majority will go out and vote and it will be a gigantic expression of change."

Lopez was jailed in 2014 for leading protests against Maduro, and was released to house arrest in 2017. He was a mentor to opposition leader Juan Guaido, who tried to spark a military revolt against Maduro.

"We ask the Human Rights Council, the U.N., and the countries present to pay maximum attention to what is happening in Venezuela," Lopez said. "There is a gigantic opportunity for Venezuela to transition to democracy."

If that transpires, Lopez was keen to return home.

"I am one of the 8 million Venezuelans who have had to leave during the last 10 years," he said. "A transition to democracy will give us the opportunity to return."

  - Reuters