Venezuela opposition leader Corina Yoris is blocked by electoral board from registering to run for president as U.S urges incumbent Nicolas Maduro to allow all candidates to run

An opposition coalition has been left without anyone to challenge President Nicolás Maduro in the July general elections after its main candidate was blocked by the electoral board from registering to vote.

Corina Yoris, 80, was tapped last week by the Democratic Unity Roundtable last week to challenge Maduro after the country's high court banned opposition leader María Corina Machado from seeking public office.

However, Yoris was unable to enter the electoral commission's online system to register as a candidate before Monday's deadline expired.

“The will of the Venezuelan people who want a change in this country is being violated,” the presidential hopeful told reporters. 

Despite not being able to access the electoral platform, Machado vowed that Yoris will challenge the incumbent Maduro, who has served as president since 2013.

'Our candidate is Corina Yoris,' Machado told journalists on Tuesday morning.

Venezuela's aspiring opposition presidential candidate Corina Yoris was blocked Monday by the country's electoral authority from registering her vote as a candidate for the July 28 elections and challenge President Nicolás Maduro

President Nicolás visited the National Electoral Council in Caracas on Monday and registered his candidacy for the July elections. The 61-year-old communist leader has been in power since 2013 following the death of President Hugo Chávez 

Zulia Governor Manuel Rosales registered prior to Monday's deadline and could be an option to replace Yoris if Machado and the opposition front decides to form an alliance with him.

'The country is processing a huge disappointment,' Machado said. 'We will not be moved from an electoral process where Venezuelans can freely choose to elect who they want, not who is imposed by the regime.'

Rosales, who some in the opposition say has become too close to the ruling party during his governorship, belongs to the A New Time party, which until Monday had backed Machado.

'I had to take a decision, it was either open a space for Venezuelans to vote or go to abstention and Maduro stays six more years there without doing anything,' Rosales told reporters on Tuesday about his eleventh-hour registration.

He did not respond clearly to questions about how he was able to register when others were not.

It was predictable that the Maduro government would restrict the possibilities for the opposition to participate in the elections, said political consultant Piero Trepiccione, who added that voters want change.

'What obviously opens up now is a period of negotiation, of understandings, of deals to see if the candidates stay or are substituted by others,' said Trepiccione, referring to Rosales and Enrique Marquez, a former member of the national electoral council who registered as an independent.

Parties have until April 20 to name any substitutes for registered candidates.

Venezuelan opposition leader Maria Corina Machado was barred by the country's top court from holding public office and challenging incumbent President Nicolás Maduro in the July elections

Venezuela President Nicolás Maduro addresses supporters during a rally Monday after he officially announced he would seek his third term in ofice

Some of the opposition may back Rosales, said analyst Ricardo Rios, who runs the Poder and Estrategia consultancy in Caracas, while others may continue pushing for election guarantees.

'While they seek those electoral conditions time will pass and it will become reality that they don't participate (in the vote),' he said.

'Rosales alone cannot channel electoral energy (for the opposition), he needs the support of other consolidated parties and principally Maria Corina,' said Oswaldo Ramirez, director of ORC Consultancy.

The ruling party has not commented on the inability of Yoris to register, but the electoral council is expected to confirm the identities of 13 people who have registered for the election on July 28.

Maduro, a 61-year-old former bus driver, successfully registered on Monday to seek a second re-election July 28 for another six-year term.

The arrests of close Machado allies last week, as well as the issue of warrants for the capture of seven others, prompted international outcry.

The United States started re-imposing sanctions and warned about the April expiry of oil sanctions relaxations after Machado's public office ban, imposed over her support of U.S. sanctions and accusations of corruption that she denies, was upheld in January.

A White House National Security Council spokesperson said the U.S. was deeply concerned that Yoris was unable to register and was working with other members of the international community to ensure Venezuelans could participate in inclusive and competitive elections.

'As we stated in January, we are committed to maintaining sanctions relief if Maduro upholds the commitments outlined in the agreed-to Barbados electoral roadmap,' the spokesperson said, referring to the October electoral deal that originally led the U.S. to relax some sanctions.

Venezuela's neighbors Colombia and Brazil, which both have leftist presidents, each expressed concern in their own statements, urging compliance with the electoral deal.

'With the deadline for registering candidates for the Venezuelan presidential elections having passed, last night, 3/25, the Brazilian government is following with expectation and concern the development of the electoral process in that country,' Brazil's Ministry of Foreign Affairs said in a statement Tuesday.