WASHINGTON/MOSCOW (Reuters) - The United States and Russia traded warnings against interfering in Venezuela on Wednesday, a day after U.S. Secretary of State Mike Pompeo accused Moscow of stopping President Nicolas Maduro from leaving the country.

U.S. Secretary of State Mike Pompeo attends a news conference at a warehouse where international humanitarian aid for Venezuela is being stored, near La Unidad cross-border bridge between Colombia and Venezuela in Cucuta, Colombia April 14, 2019. REUTERS/Luisa Gonzalez

Russian Foreign Minister Sergei Lavrov told Pompeo by phone that further “aggressive steps” in Venezuela would be fraught with the gravest consequences, the Russian ministry said.

“The Russian side underlined that interference by Washington in the internal affairs of a sovereign state and threats towards its leadership was a flagrant breach of international law,” the ministry said.

The U.S. State Department said Pompeo urged Russia in the call to stop supporting Maduro. He also “stressed that the intervention by Russia and Cuba is destabilizing for Venezuela and for the U.S.-Russia bilateral relationship,” it said.

On Tuesday, Pompeo accused Russia of intervening to persuade Maduro to abandon a plan to leave the country following a call by opposition leader Juan Guaido for Venezuela’s military to help him oust Maduro.

Russia rejected that allegation on Wednesday, with foreign ministry spokeswoman Maria Zakharova calling it “fake news.”

The United States has criticized Russia and Cuba for working to prop up Maduro. Russia, which has supplied Venezuela with weapons and loans, says the United States is trying to encourage a coup in the Latin American country.

While Pompeo said earlier Wednesday that the United States was prepared to take military action if necessary, Pentagon officials told Congress they had not been given orders to prepare for war.

“Military action is possible. If that’s what’s required, that’s what the United States will do,” Pompeo told Fox Business Network.

U.S. officials continue to stress that they prefer a peaceful transition in the country.

Marchers gathered on Wednesday for planned mass street protests against Maduro.

Asked if Washington was considering more sanctions against Russia because of the situation, National Security Adviser John Bolton told reporters the National Security Council would meet to discuss Venezuela on Wednesday. “We’ll be considering a lot of steps,” he said.

Bolton would not elaborate on what the United States knew about its accusations that Russia was influencing Maduro’s plans, but he said Moscow’s interference was not welcome.

“This is our hemisphere,” Bolton said. “It’s not where the Russians ought to be interfering. This is a mistake on their part. It’s not going to lead to an improvement of relations.”

Acting U.S. Defense Secretary Patrick Shanahan canceled a planned trip to Europe on Wednesday to help him better coordinate with the Trump administration on Venezuela as well as on deployments to the U.S. border with Mexico, the Pentagon said.