President Barack Obama urged Venezuela Wednesday to release protesters detained in anti-government demonstrations that turned violent and address the "legitimate grievances" of its people.
Obama condemned violence that has marred two weeks of protests in the oil-rich country against the leftist government of President Nicolas Maduro, with four people killed so far.
Opposition leader Leopoldo Lopez, one of the main actors in the wave of protests, is due for a hearing at the prison where he is held on claims he incited the violence.
Scores of protesters have also been detained.
"Along with the Organization of American States, we call on the Venezuelan government to release protesters it has detained and engage in real dialogue," Obama told reporters after a North American leaders summit in this Mexican city.
Speaking about unrest in Venezuela and Ukraine, Obama denounced the "unacceptable violence in those two countries which the United States strongly condemns."
"In Venezuela, rather than trying to distract from its own failings by making up false accusations against diplomats from the United States, the government ought to focus on addressing the legitimate grievances of the Venezuelan people," Obama said.
"All parties have an obligation to work together to restrain violence and restore calm."
Venezuela's relations with Washington, long strained under stalwart leftist leader Hugo Chavez, have remained sour and distrustful under Maduro, who has stuck closely to his predecessor's policies.
About 100 supporters of jailed opposition leader Lopez rallied Wednesday outside a Caracas court where he had been due to hear charges blaming him for a deadly episode of violence.
Heavy security surrounded the Palace of Justice, blocking streets leading to the building, where the Harvard-educated economist had been scheduled to appear after spending the night in jail.
But his party said in a Twitter message that the hearing had been moved to a military jail. Lopez's defense attorney Juan Carlos Gutiérrez said a court illegally ordered the change claiming it would protect Lopez's life.
Lopez's dramatic surrender to national guard troops at a protest rally Tuesday came after two weeks of protests in the oil-rich country against the leftist government of President Nicolas Maduro.
Maduro is under fire over what critics say is rampant crime, runaway inflation, high unemployment and other economic problems.
After three people were killed in street clashes on February 12, Maduro ordered Lopez's arrest, blaming him for the violence.
Political scientist Angel Oropeza said the government was walking a tightrope.
"They may hold him for a few days. If they free him right away, it would be a sign of weakness," said Oropeza, a political science professor at Simon Bolivar University in Caracas.
"But if they hold on to him for a long time, it could fuel the protests even more and the government would come under more international pressure," he said.
Oropeza said that with the arrest, the only thing the government had achieved was to divert people's attention away from Venezuela's economic woes and "shift debate to an area it has always handled better — that of political confrontation."
On Tuesday, Lopez told thousands of his supporters, all clad in white, that he hoped his arrest would highlight the "unjust justice" in Venezuela. He drew an explosion of cheers from the crowds.
Maduro, speaking to pro-government oil workers dressed in red in the western part of Caracas, countered that Lopez would have to "answer for his calls to sedition."
Lopez, draped in a Venezuelan flag, suddenly emerged in the crowd on Tuesday on the Plaza Brion, climbing a statue of Cuban independence hero Jose Marti.
After delivering a brief message to his cheering supporters, who had defied a ban on the march, he surrendered to the National Guard.
"I present myself before an unjust justice, before a corrupt justice," said Lopez.
"If my incarceration serves to wake up people... it will have been worth it."
He calmly walked under escort to a National Guard vehicle as his supporters pressed around the vehicle, blocking its path.
Maduro's government summoned its followers to rallies of its own in an area of downtown Caracas, amid fears of clashes with the opposition demonstrators.
The tensions generated by the protests have spilled into the international arena.
On Sunday, Maduro ordered the expulsion of three US diplomats, accusing them of meeting student leaders under the guise of offering them visas.
State Department deputy spokeswoman Marie Harf said that the United States was still mulling its options.
"I would repeat very strongly that the allegations against our diplomats by the Venezuelan government are baseless and false, and that right now, we are considering what actions to take," Harf said.