Venezuela's opposition leader Juan Guaidó has told tens of thousands of his supporters that humanitarian aid will be brought in, despite opposition from President Nicolás Maduro.
He also told a rally in Caracas that "the usurper [Maduro] has to leave".
Mr Maduro earlier told the BBC he would not allow aid in as it was a way for the US to justify an intervention.
The US and most Western governments have recognised Mr Guaidó as interim president.
Mr Maduro, who is backed by Russia and China, is under growing pressure to call early presidential elections amid a worsening economic crisis and accusations of widespread corruption and human rights violations.
What did Mr Guaidó say?
Mr Guaidó told his supporters in the capital that humanitarian aid would be brought into Venezuela on 23 February.
"We have almost 300,000 Venezuelans who will die if the aid doesn't enter. There are almost two million whose health is at risk."
Last week, the first lorries with US humanitarian aid for Venezuela arrived in the Colombian border city of Cúcuta.
The vehicles were parked near the Tienditas bridge, which remains blocked by Venezuelan troops.
What about Mr Maduro's interview?
Speaking to the BBC's Orla Guerin, Mr Maduro called US President Donald Trump's government a "gang of extremists" and blamed America for his country's crisis.
He also reiterated that he would not allow US humanitarian aid into Venezuela.
"They are warmongering in order to take over Venezuela," he said.
Mr Maduro - who still has the support of Turkey, Russia and China and, crucially, of the Venezuelan army - said he did not see the need for early presidential elections.
"What's the logic, reasoning, to repeat an election?" he asked.
Relations between the US and Venezuela were already fraught before President Donald Trump's administration became one of the first to back Mr Guaidó as interim leader.
Venezuela broke off diplomatic relations in response while Mr Trump said the use of military force remained "an option".
The US, which accuses Mr Maduro's government of human rights violations and corruption, has led the international pressure on the Venezuelan president to step down.
It has imposed a raft of economic measures on the country, including against the state-owned oil company PDVSA, aiming to hit Venezuela's main source of revenue.
In recent years the US has frozen Mr Maduro's US assets, restricted Venezuela's access to US markets and blocked dealings with those involved in the country's gold trade.
For years Venezuelans have faced severe shortages of basic items such as medicine and food. Last year, the inflation rate saw prices doubling every 19 days on average.
Three million people, or 10% of the population, have left the country since the economy started to worsen in 2014, according to the UN.
What's the background to this?
Mr Maduro, who has been in power since 2013, was re-elected to a second term last year.
But the elections were controversial, with many opposition candidates barred from running or jailed, and claims of vote-rigging.
The head of the opposition-controlled National Assembly, Mr Guaidó declared himself president on 23 January.
He said the constitution allowed him to assume power temporarily when the president was deemed illegitimate.
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