Nicolas Maduro, Venezuela's embattled president, told Russian state media he's ready to negotiate with the country's opposition and claimed he's in talks to set up international mediation to help resolve the crisis.

But hours later, his offer was rejected by opposition leader Juan Guaidó, who said he would only engage in dialogue with the "real holders of power" in the country and said Maduro was the only person responsible for the humanitarian crisis in the country.

Guaidó, the president of the National Assembly who was sworn in as interim president last week among thousands of supporters, addressed crowds again Wednesday at a hospital in Caracas. Thousands of people joined his call for national protests, taking to the streets in a national walkout, and supporters cheered at him, "Guaidó is here, Guaidó is here, hope is here!"

In an interview with Russian state news agency RIA Novosti Wednesday, Maduro said his foreign minister was in negotiations with several countries and that the question of international mediation could be resolved in the "coming hours."

"I am ready to sit at the negotiating table with the opposition, so that we can talk for the good of Venezuela, for peace and its future," Maduro said.

But Guaidó's new envoy to the U.S., Carlos Vecchio, accused Maduro of manipulating the word "dialogue" and using the offer to talk to "gain oxygen and stay in power."

"We're not for engaging in a dialogue on Maduro's terms," he said in Washington Wednesday. "We're not going to be a part of that. Our agenda is very clear –- how to negotiate the exit of this dictator in Venezuela."

The Trump administration, the first international government to recognize Guaidó as interim president, has been a key part of pushing for that exit, leading to accusations from Maduro and his allies like Russia that the U.S. is behind a coup.

President Donald Trump spoke to Guaidó on Wednesday, calling to "congratulate him on his historic assumption of the presidency and to reinforce President Trump's strong support for Venezuela's fight to regain its democracy," according to a White House readout of the call.

Venezuelan President Nicolas Maduro talks during a meeting with Venezuelan diplomats returning from the US, at the Miraflores presidential palace in Caracas, Jan. 28, 2019.(Venezuelan Presidency/AFP/Getty Images) Venezuelan President Nicolas Maduro talks during a meeting with Venezuelan diplomats returning from the US, at the Miraflores presidential palace in Caracas, Jan. 28, 2019.

The call took place mere hours after Maduro's attorney general announced he was opening a criminal probe into Guaidó, and requested that he be banned from leaving the country. Venezuela's Supreme Court granted the request from the attorney general, Tarek William Saab, who accused Guaidó of "undermining the peace of the nation."

Maduro told RIA Novosti Wednesday he was not aware yet whether an order for Guaidó's arrest had been issued, though he said it was his opinion a "state coup" was underway.

When asked whether he fears for his safety, Guaidó told supporters, "Here we are, and here I'll continue to be."

In a tweet early Wednesday morning, Trump said Guaidó is being "targeted" by the Supreme Court. He warned Americans not to travel to Venezuela until further notice.

Venezuela has been locked in a standoff between the two leaders since the National Assembly swore Guaido in as president, backed by the United States and several other countries that have recognized him. So far, Venezuela's military has backed Maduro, as international calls for Maduro to step down have grown and the U.S. has intensified efforts to force him out of power.

Maduro said in the Russian interview he'd sent letters to several governments proposing they help start a dialogue. He didn't say which countries he was in talks with but did name some that have shown "sincere concern" for Venezuela -- Mexico, Bolivia, Uruguay and Russia -- as well as the Vatican and unspecified "European countries."

Venezuela's National Assembly head and self-proclaimed "acting president" Juan Guaido raises his hand to vote for the candidates he wants to be appointed as ambassadors in the countries that recognized him as Venezuela's interim president, at the National Assembly in Caracas, Jan. 29, 2019.(Yuri Cortez/AFP/Getty Images) Venezuela's National Assembly head and self-proclaimed "acting president" Juan Guaido raises his hand to vote for the candidates he wants to be appointed as ambassadors in the countries that recognized him as Venezuela's interim president, at the National Assembly in Caracas, Jan. 29, 2019.

"At this stage, we're talking about private negotiations, negotiations by phone between presidents, heads of foreign ministries," Maduro said. "Our minister of foreign affairs is very active. We hope for good results in the coming hours."

Maduro also said he wished to talk with Trump but was doubtful of that prospect because John Bolton, a U.S. national security adviser, likely wouldn't allow it.

International support for Maduro and Guaidó has coalesced along familiar Cold War fault lines, with Russia, China and other formerly socialist countries backing Maduro and many Western nations siding with Guaidó. The leaders of France, Belgium, Germany and Spain on Saturday gave Maduro eight days to call new elections or they would back Guaidó.

Maduro told RIA Novosti that he was open to new parliamentary elections in the National Assembly, the opposition-controlled parliament of which Guaidó is the speaker, but demurred on a new presidential vote, saying his election was legitimate.

Sergey Lavrov, Russia's foreign minister, called on the opposition to negotiate with Maduro and to seek international mediation on Wednesday.

A woman walks under the snow past a banner in the Spanish Navarra village of Leitza, Jan. 30, 2019.(Ander Gillenea/AFP/Getty Images) A woman walks under the snow past a banner in the Spanish Navarra village of Leitza, Jan. 30, 2019.

Moscow has emerged as Maduro's strongest public backer, accusing the U.S. of seeking illegal regime change. Russia has invested billions of dollars in Venezuela in recent years, providing crucial loans to prop up its economy in addition to military hardware.

Last week there were reports private Russian military contractors had been dispatched to bolster Maduro's security.

Maduro on Wednesday refused to comment on those reports, which Russia has denied.

"No comment," he said in English. "I am commenting nothing on this."

Efforts to remove Maduro this week have shifted to increasing economic pressure on the nation, with the U.S. this week sanctioning Venezuela's state oil company, PDVSA. The sanctions shut down Maduro's access to revenues from oil exports to the U.S., a critical source of cash for a country already suffering an economic meltdown.

Venezuela is set to lose billions in exports over the next year, making it difficult to repay debts to Russia and even larger ones to China.

U.S. National Security Adviser John Bolton as he waits to address reporters in Washington, D.C., Jan 28, 2019.(Jim Young/Reuters) U.S. National Security Adviser John Bolton as he waits to address reporters in Washington, D.C., Jan 28, 2019.

Fear of bloodshed in Venezuela has also continued to rise. Guaidó has called on the military to join him, but so far top commanders have publicly sided with Maduro, with scattered defections among diplomats and military attaches stationed abroad.

The Trump administration has not ruled out military intervention in Venezuela, and Bolton stoked that speculation on Tuesday when cameras picked up on a notepad on which he'd scrawled "5,000 troops to Colombia."

Maduro dismissed Bolton's note, telling RIA Novosti it was "clownery" and "stupid childish games."

But Vecchio, Guaidó's new envoy in Washington, said that their government was not interested in U.S. military support and that the only conversations they have had with the U.S. have been about humanitarian aid and coordinating international recognition of Guaidó.

"We haven't talked about any other options. We haven’t talked about any other options," he said Wednesday.

ABC News's Davi Merchan contributed to this report from Cúcuta, Colombia.