WASHINGTON — President Trump has signed a new executive order imposing sanctions on Venezuela, further isolating the regime of Nicolás Maduro as it cracks down on democratic protests sweeping the oil-rich but cash-poor South American country.

It's the fourth round of U.S. sanctions this year on Maduro and his inner circle, 30 of whom have had their U.S. assets seized.

"This order demonstrates more clearly than ever that the United States will not allow an illegitimate dictatorship to take hold in the Western Hemisphere at the expense of its people," National Security Adviser H.R. McMaster said Friday.

The executive order was signed Thursday but not immediately disclosed until after it went into effect at midnight Friday — a tactic designed to prevent sanctions evasion.

The new sanctions are an attempt to close a number of loopholes Venezuela has used to sell off assets and raise money. They restrict the ability of Venezuela and state-owned oil company PDVSA to issue new debt or stock in U.S. dollars, or engage in other financial dealings with U.S. citizens.

The order allows the Treasury Department to make exceptions, and the Office of Foreign Assets control made four of them on Friday. They allow for a 30-day wind-down period, trading of existing bonds on the secondary market, and transactions involving food, medicine and humanitarian aid. The oil refiner Citgo — owned by Venezuela but based in Houston — is also exempt.

"We want to make sure that U.S. pensions or U.S. fiduciaries are not hurt by this, and if they want to sell their bonds they can do so," Treasury Secretary Steven Mnuchin said. "But this will limit any new investments."

The sanctions come two days after Vice President Pence met with Venezuelan exiles in Miami, promising them that "we are with you and we will stand with you until democracy is restored in Venezuela."

Trump has even raised the possibility of military action in Venezuela, although the White House seems to have focused more on economic and diplomatic sanctions.

"In terms of military options or other options, there's no such thing any more as only a diplomatic option, or only a military option, or only an economic option. We try to integrate all the options together," McMaster said Friday. But he continued, "No military options are anticipated in the near future."

Maduro, the 54-year-old successor to former socialist dictator Hugo Chavez, has faced widespread protests following an economic collapse caused by a decline in oil prices, runaway inflation and severe shortages of basic goods.

The Venezuelan president has attempted to keep his grip on power by holding new elections — which were plagued by strongarm tactics and counting irregularities — and rewriting the nation's constitution.

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