WASHINGTON (Reuters) - U.S. President Donald Trump is considering imposing sanctions on companies from other countries that do business with Venezuela to cut off revenues to President Nicolas Maduro, Trump’s national security adviser John Bolton told Reuters TV on Friday.

“We’re moving exactly in that direction,” Bolton said when asked whether Trump would consider what are known as “secondary sanctions.”

“We are even now looking at a series of additional steps we could take,” Bolton said in the interview.

The United States and most other Western countries have thrown their backing behind Venezuelan opposition leader Juan Guaido, who invoked the constitution in January to declare himself interim president, arguing that Maduro’s 2018 re-election was illegitimate.

Oil provides 90 percent of export revenue for OPEC member Venezuela. The United States imposed sanctions on Venezuela’s state-owned oil company PDVSA in January, preventing U.S. companies from dealing with it unless revenues went to a fund available to Guaido.

The Trump administration has not yet slapped sanctions on companies from other countries that do business with PDVSA - but U.S. officials have been having “conversations” with oil trading houses and governments around the world to convince them to scale down their dealings with Maduro, Trump’s Venezuela envoy Elliott Abrams said earlier on Friday.

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MONROE DOCTRINE

Russia and China support Maduro, who has said Guaido is a puppet of Washington. Maduro retains control of state functions and the loyalty of the country’s military.

Bolton said he was not concerned that the push to oust Maduro was losing momentum.

“I can tell you there’s a lot going on beneath the surface. The opposition is in constant contact with large numbers of admirals and other supporters within the Maduro administration,” Bolton said.

“It’s a struggle against an authoritarian government and it’s obviously going to take some time,” he said.

Trump is looking at options - including sanctions - to respond to Russia’s growing military presence in Venezuela, Bolton said. Two Russian air force planes carrying nearly 100 military personnel landed outside Caracas on Saturday.

“We’re not afraid to use the phrase ‘Monroe Doctrine’ in this administration,” Bolton said, referring to the 1823 policy established by then-President James Monroe, widely seen in Latin America as a justification for U.S. armed intervention in the region.

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“And one of the purposes of the Monroe Doctrine was to prevent foreign interference and even recolonization,” Bolton said.

“If you look at the presence of Cuban and Russian forces in Venezuela, you have to ask when will the people of Venezuela get to choose their government rather than foreigners?” he said.

Venezuela’s economic crisis, which has caused shortages of food and medicine, has pushed millions of people to flee the country.

Trump is considering granting temporary protection from deportation to the more than 70,000 Venezuelans believed to be in the United States, but wants to focus first on ensuring there is a transition in the government of the country, Bolton said.

“We want to be sure that people are not put back into a difficult position if they’re opponents of the Maduro regime. On the other hand, there are many families of Maduro regime supporters in this country that wanted out of Venezuela to be safe,” Bolton said.