The U.S. Treasury’s Office of Foreign Assets Control (OFAC) announced a ban in early February on the use of its financial system in oil deals with Venezuela after April.

But as recently as this week, the U.S. State department has called up foreign firms to say that the scope of the sanctions is wider.

Sources say that the State Department made clear that any kind of oil trade, whether it be direct, indirect or barter, would be considered a breach.

Washington has been using its oil clout more and more. At a major oil event in Houston this month, U.S. Secretary of State Mike Pompeo made a rare appearance and laid out a vision of working with energy firms to isolate Iran and Venezuela.

The biggest trading firms, based in Europe, such as Vitol, Gunvor, Mercuria, Trafigura and Glencore account for about 10 percent of global oil trade.

Venezuela’s overall exports of crude and fuel dropped to 920,000 barrels a day in the first month of sanctions from more than 1.5 million bpd in the prior three months, according to Refinitiv Eikon and state firm PDVSA data.

Russia, however, remains a staunch supporter of Maduro’s government as Venezuela plunges into an economic and humanitarian crisis.

In an escalation of tensions, U.S. President Donald Trump called on Moscow to remove all its soldiers from Venezuela after a Russian military contingent arrived just outside of Caracas, saying “all options” were open to make that happen.

Russia responded on Thursday saying it had sent “specialists” to Venezuela under a military cooperation deal.

Russian military specialists are in Venezuela to service pre-existing contracts for the supply of Russian arms, Kremlin spokesman Dmitry Peskov says. 

Peskov also says Russia is not interfering in Venezuela's internal affairs and that the Kremlin hopes other countries would let Venezuelans decide their own fate.

Two Russian air force planes landed outside Caracas on Saturday carrying nearly 100 Russian troops.

"Russia has to get out," Trump tells reporters during a meeting with the wife of Venezuelan opposition leader Juan Guaido.

Asked how that could be accomplished, Trump says: "We'll see. All options are open."