U.S. President Donald Trump imposed a freeze on all Venezuelan government assets in the United States on Monday, sharply escalating a diplomatic and sanctions drive aimed at removing socialist President Nicolas Maduro from power.

The executive order signed by Trump goes well beyond the sanctions imposed in recent months against Venezuela's state-run oil company PDVSA and the country's financial sector, as well as measures against dozens of Venezuelan officials.

"All property and interests in property of the government of Venezuela that are in the United States ... are blocked and may not be transferred, paid, exported, withdrawn, or otherwise dealt in," according to the executive order released by the White House.

The scope of the announcement came as a surprise even to some Trump administration allies. "This is big," said Ana Quintana, senior policy analyst with the Heritage Foundation, a conservative Washington think-tank.

Quintana said it appeared the order would be a sweeping embargo on doing business with Venezuela, although she was awaiting further details.

A statement from Venezuela's Foreign Ministry called the move an effort to "formalize a criminal economic, financial, and commercial blockade that has already started."

National Security Adviser John Bolton and U.S. Commerce Secretary Wilbur Ross at the summit in Lima, Peru, discussing the crisis in Venezuela. (Guadalupe Pardo/Reuters)

The United States and most Western nations have called for Maduro to step down and have recognized Venezuelan opposition leader Juan Guaido as the country's legitimate president.

Guaido appointed a board for Citgo Petroleum, Venezuela's most important foreign asset, earlier this year.

'Maduro is at the end of his rope'

China and Russia have continued to back Maduro, prompting U.S. national security adviser John Bolton to warn the two countries on Monday against doubling down in their support for him.

Addressing a summit on Venezuela in the Peruvian capital Lima, Bolton stressed that U.S. authorities can now target and sanction anyone, including foreigners, who supports Maduro's government.

"We are sending a signal to third parties that want to do business with the Maduro regime: proceed with extreme caution," he said.

Bolton called for tougher international action against Maduro, whom he accused of only pretending to engage in negotiations with the opposition to buy himself time.

"The time for dialogue is over. Now is the time for action. Maduro is at the end of his rope," Bolton said, warning Russia not to provide him with further support. "We will ensure that Maduro runs out of ways to financially sustain himself."

Trump said on Thursday he was considering a quarantine or blockade of Venezuela, although he did not elaborate at the time on when or how such a blockade would be imposed.

He is taking more dramatic action after numerous rounds of sanctions failed to turn Venezuela's military against Maduro or make significant progress in dislodging him.

U.S. officials have long said they had other weapons in their economic arsenal, even as they privately expressed frustration that European partners and others had not taken stronger steps and that the months-long pressure campaign had not made more headway.