Millions of Venezuelans are expected to go to the polls as they decide whether to back President Nicolas Maduro's plan to create a so called "constitutional super-body" on Sunday 30 July. But opposition organisations to the ruling socialist party are boycotting the crucial vote, claiming that it will be rigged in Maduro's favour. The poll comes after days of violence in Caracas, the capital of the South American state.

At least 100 people have been left dead following skirmishes between anti-government activists and riot police. Maduro, who succeeded Hugo Chavez in 2013, has seen his popularity fall as the Venezuelan economy suffers under a drop in oil prices. The financial and social turmoil has even seen the country hit with a toilet paper shortage.

The opposition parties are worried that Maduro will use the new assembly to rewrite Venezuela's constitution and overrule the state's congress, where the government is outranked by opposition members.

The US has pulled its diplomats out of Venezuela amid the unrest, while British Foreign Secretary Boris Johnson has urged the Venezuelan government to refrain from "divisive and inflammatory" action.

"Including the plan to form a Constituent Assembly later this month," Johnson said. "This will only further undermine confidence in the country's democracy. Human rights, the rule of law, the separation of powers and the integrity of democratic institutions must be respected.

"The UK joins with the Vatican, the neighbours of Venezuela and our European friends to urge the government to enter constructive talks with the Opposition. I call on President Maduro to change course and break the deadlock for the benefit of all Venezuelans."

US Vice President Mike Pence spoke to Venezuelan opposition leader Leopoldo Lopez over the phone on Friday 28 July.

"On behalf of President Trump, the Vice President firmly stated that the United States stands with the Venezuelan people, and praised Lopez for his courage and outspoken defence of Venezuelan democracy despite his current detention under house arrest," a White House spokesperson said.

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"Vice President Pence once again called for the full and unconditional release of all political prisoners in Venezuela, free and fair elections, restoration of the National Assembly, and respect for human rights in Venezuela.

"The Vice President also reiterated President Trump's pledge that if the Maduro regime imposes its Constituent Assembly on Sunday, July 30, the United States will respond with strong and swift economic actions."

The US serves as the largest market for Venezuela's oil exports. But Donald Trump's administration slapped economic sanctions on 13 top Venezuelan officials on 26 July.

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