The Maduro regime in Venezuela is under fire after it blocked aid from entering the country from the Colombian border.
United States Secretary of State Mike Pompeo blasted embattled President Nicolás Maduro demanding the border be reopened.
"The Venezuelan people desperately need humanitarian aid," he posted to Twitter.
"The US and other countries are trying to help, but Venezuela's military under Maduro's orders is blocking aid with trucks and shipping tankers.
"The Maduro regime must let the aid reach the starving people."
Mr Pompeo also posted a photo of the Tienditas Bridge that appeared to show two large blue containers and an orange tanker blocking the crossing.
The three-lane bridge connects Cucuta, Colombia, with Venezuela.
Cucuta is one of three places where international aid is collected as a crippling economic crisis sweeps Venezuela.
Venezuela's Opposition Leader and self-declared president Juan Guaido has made desperate pleas for aid from the international community.
Mr Guaido sparked an international crisis on January 23 when he declared himself acting president — with the US and other countries recognising him as the legitimate leader.
Other countries including Russia and China have refused to do so.
The move to barricade the border was a clear challenge to a US-backed effort by the opposition to bring humanitarian aid into a nation plagued by shortages of food and medicine.
The Trump administration has pledged $20 million in aid and Canada has promised another $53 million.
The aid squabble is the latest front in the battle between Mr Guaido and Mr Maduro, who is vowing not to let the supplies enter the country. Maduro argues Venezuela isn't a nation of "beggars" and has long rejected receiving humanitarian assistance, equating it to a foreign intervention.
Venezuelan Jose Mendoza stood at the entrance to the Colombian side of the bridge holding a sign that said: "Humanitarian aid now." Mendoza, 22, said he was tired of seeing Venezuelans suffer from food and medical shortages, and the military should stand on the side of suffering Venezuelans.
"They have to be by the side of the people and support us," Mr Mendoza said. "They have family members who are dying of hunger. The call is for them too." Roughly 40 countries around the world have backed Mr Guaido, who swore himself in as president in late January contending that as head of the opposition-led National Assembly he is Venezuela's rightful leader because Mr Maduro's re-election last year was a sham.
Mr Guaido says the emergency shipment is a "test" for Venezuela's armed forces, which will have to choose if they allow the much-needed aid to pass or obey orders. No details have been released on exactly how the opposition plans to get the shipments into Venezuela.
Soaring hyperinflation has forced millions of Venezuelans to flee or go hungry as they struggle to find or afford basic goods and medicine. Mr Maduro appeared on state TV on Wednesday evening wearing a white lab coat to demonstrate what he considers Venezuela's modern healthcare system in clinics countrywide — without mentioning attempts to block medical supplies at the border.
"The revolution is more alive than ever," Mr Maduro said. "We're advancing in the development of healthcare for the good of the people."
An emphatic Mr Pompeo said Venezuelans desperately needed the emergency supplies the US and other countries were preparing to provide.
CRISIS IN VENEZUELA
Once one of the richest countries in South America, Venezuela has long been hurtling towards economic, social and institutional collapse, according to aid group Mercy Corps.
Nearly 90 per cent of the country's people live below the poverty line.
Out-of-control hyperinflation has exacerbated acute food and medical shortages.
The crisis started in 2010 under then-president Hugo Chavez and is considered the worst economic disaster in Venezuela's history.
Critics have blamed Mr Chavez's populist policies.
Widespread corruption and economic mismanagement have also been blamed.
The country is deeply reliant on oil exports and was hit hard when prices collapsed in 2015.
Basic items have become almost impossible to find.
Venezuelan journalist Nayrobis Rodriguez wrote she spent seven days hunting for somewhere to buy a toilet roll in the city of Cumana.
The Washington Post has outlined the horror of daily life in Venezuela, including prison inmates foraging for dead rats, pumas and lions wasting away in Venezuelan zoos, and mothers embarking on harrowing cross-border trips just to find medicine for their children.
There are almost no medical supplies in some hospitals, with doctors reportedly being robbed as they take the stairs to different levels. The lifts have long stopped working.
More than 10 million — about 10 per cent — of the population has already left the country.