Cúcuta (Colombia) (AFP) - Trucks carrying desperately-needed humanitarian aid for crisis-wracked Venezuela arrived at its border with Colombia on Thursday as ministers from more than a dozen European and Latin American countries called on socialist leader Nicolas Maduro to hold "free" presidential elections.

The International Contact Group meeting in Montevideo said it was committed to finding a "peaceful, democratic" way out of the power struggle between Maduro and opposition rival Juan Guaido "without the use of force."

That coincided with the arrival at Colombia's border with Venezuela of the first trucks bearing US humanitarian aid.

Several vehicles loaded with food and medicines rumbled into a collection center on the Colombian side of the Tienditas border bridge, which remains blocked by Venezuelan troops, heightening tensions with Washington.

The convoy, which departed the day before from the city of Bucaramanga in northeastern Colombia, was cheered on its arrival by a group of Venezuelan migrants.

- Tense standoff -

Claiming his legitimacy from the constitution, Guaido -- the 35-year-old National Assembly leader -- stunned Venezuelans when he proclaimed himself interim president on January 23, setting up a tense standoff with Maduro. Both men called huge rival rallies onto the streets.

Guaido is trying to force from power the socialist leader -- labeled a dictator by the West and his Latin American neighbors after presiding over Venezuela's economic collapse -- aiming to set up a transitional government and hold new presidential elections.

Venezuelan migrants gathered at the Colombian town of Cucuta to see if they could receive some of the aid arriving at the border and being stockpiled in nearby warehouses.

Yajaira Gonzalez, 64, said she was begging Maduro to let through the aid -- food, medicine and personal hygiene kits -- to her desperate compatriots back home.

"Mr. President, we are not OK. We are suffering," she said, referring to Maduro.

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Gonzalez said she used to be a Chavista -- a supporter of Maduro's predecessor, the late socialist firebrand Hugo Chavez -- but not anymore.

Dajelys Lopez crossed from the other side of the border with her baby in a stroller to see if she could find in Cucuta what she cannot get in Venezuela.

"Yesterday a friend died because he suffered a seizure and did not have medication to deal with it," Lopez said.

- 'Chaotic and dangerous' -

In the Uruguay capital, at the first international forum to deal with the crisis, EU foreign policy chief Federica Mogherini urged a peaceful solution to avoid a "chaotic and dangerous" unravelling of Venezuelan society.

Following five hours of talks, the group announced it would send a technical mission to Venezuela to "establish the necessary guarantees for a credible electoral process, as soon as possible," and to allow in humanitarian aid.

Dozens of pro-Maduro supporters protested outside the meeting against US intervention in the country.

Elliot Adams, the US envoy to Venezuela, criticized the Contact Group and urged all countries to shut out Maduro and deal "solely" with Guaido's "legitimate government."

In Washington, Brazil's foreign minister Ernesto Araujo described the Contact Group's call for elections as "not very useful," claiming they wouldn't be fair.

Guaido -- recognized as interim president by more than 40 countries including the US -- has appealed to the army to side with him and forsake "a dictatorship that does not have an iota of humanity."

US Admiral Craig Faller, who heads the US military's southern command, said Venezuela's soldiers were still loyal to Maduro, despite their hardship.

"The rank and file are starving, just like their population," Faller told a Senate committee.

Maduro, who is supported by Russia, China, Turkey, Cuba and Iran, has refused all humanitarian aid shipments, saying they would open the way to allow a US military invasion. The 56-year-old has repeatedly accused the United States of fomenting a coup.

In Moscow, foreign ministry spokeswoman Maria Zakharova accused Washington of violating the UN charter on the non-use of force by repeatedly threatening Maduro.

She described sending humanitarian aid to Venezuela as "the pinnacle of cynicism".

"On the one hand, sanctions are imposed to block the Venezuelan economy, and on the other hand, humanitarian aid is proposed," she said.

- Regime to fall? -

Maduro -- having rejected an EU ultimatum on organizing snap presidential elections -- welcomed the Contact Group meeting and expressed support for "all steps and initiatives to facilitate dialogue".

But Guaido has strongly rejected any talks with the government, dismissing it as a way for Maduro to buy time.

Mogherini said the Contact Group's task was urgent because the situation inside the country was "worsening."

It was "essential to avoid internal violence and external intervention, and to open a path for a political process that leads to early elections."

Meanwhile, consultants Eurasia Group said time was running out for Maduro as Russia and China are "unlikely to lend (him) meaningful support," reinforcing its view that the socialist leader "will be unable to sustain his regime."

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