On Sunday, a day after a bold U.S. military operation in Venezuela, President Donald Trump reiterated his call for a U.S. occupation of Danish Greenland for American security interests, and his top diplomat declared that Cuba's communist regime is "in deep trouble."

The remarks by Trump and Secretary of State Marco Rubio, following the ouster of Venezuelan President Nicolas Maduro, signal a determined U.S. administration looking to play a more expansive role in the Western Hemisphere.

With veiled threats, Trump is unsettling allies and adversaries alike in the Western Hemisphere and sparking sharp questions worldwide: Who is next?

"This is a very strategically important time. We have Russian and Chinese ships all over Greenland," Trump told reporters on his flight back to Washington from his Florida home. "We need Greenland for national security. Denmark cannot handle it."

Trump told reporters, "We'll think about Greenland in two months," and then added, "We'll talk about Greenland... in 20 days."

When asked in an interview with The Atlantic on Sunday morning how the U.S. military action in Venezuela could affect Greenland, Trump responded, "They have to judge for themselves" and "I really don't know." The White House did not respond to a request for comment.

Trump outlined in the administration's national security strategy released last month "restoring American primacy in the Western Hemisphere" as a key guideline for his White House term.

Trump has also advocated an assertive approach to America's neighbors and beyond, citing the Monroe Doctrine, which rejected European colonialism in the 19th century, and the Roosevelt Corollary, which the U.S. used to justify securing the Panama Canal Zone and supporting Panama's separation from Colombia.

Trump even joked that some now refer to this foundational document of the first U.S. president as the "Don-ro Doctrine."

The midnight operation by U.S. forces in Caracas on Saturday and Trump's remarks on Sunday have amplified concerns in Denmark, which holds jurisdiction over the mineral-rich, vast island of Greenland.

Danish Prime Minister Mette Frederiksen stated that Trump has "no right to annex" the territory.

She also reminded that Denmark already provides the U.S., a NATO ally, with extensive access to Greenland through existing security agreements.

"Therefore, we strongly urge the United States to cease threatening actions against another country and its people, who is a historically close ally and not for sale," Frederiksen said.

Denmark also signed on to an European Union (EU) statement on Sunday, emphasizing that "the right of the Venezuelan people to determine the future of their country must be respected." Trump had declared he would "run" Venezuela and had pressed acting President Delcy Rodriguez to step down.

Trump, on Sunday, mocked Denmark's efforts to enhance Greenland's national security posture, saying Denmark had "added one more dog sled to the arsenal" in the Arctic territory.

He also pointed out that Greenland is filled with Chinese and Russian vessels.

Greenlanders and Danes were further angered by social media posts from Katie Miller, a podcaster from the Trump administration, after a raid, which featured a map of Greenland in the colors of the U.S. flag with the caption "Soon."

Jesper Moller Sorensen, Denmark's ambassador to Washington, responded to Katie Miller, who is married to Stephen Miller, an influential deputy White House assistant to Trump, saying, "Of course, we expect full respect for the territorial integrity of the Kingdom of Denmark."

Trump had repeatedly demanded U.S. jurisdiction over Greenland during his transition and early months back in the White House, and he did not explicitly rule out the use of military force to seize the mineral-rich, strategically important Arctic island belonging to an ally.

The issue had largely disappeared from headlines in recent months until Trump, less than two weeks ago, announced he would appoint Republican Gov. Jeff Landry of Louisiana as Greenland's envoy.

The Louisiana governor said he would assist Trump in "making Greenland part of the United States" in a volunteer capacity.

Meanwhile, concerns were mounting in Cuba, one of Venezuela's most important allies and trading partners, as Senator Rubio issued a new, stark warning to the Cuban government. U.S.-Cuban relations have been adversarial since the Cuban Revolution in 1959.

Appearing on NBC's "Meet the Press," Rubio said that Cuban officials were with Venezuelan President Maduro just before he was captured.

"The Cubans protected Maduro," Rubio said. "It was Cuban guards, not Venezuelan guards, who protected him." The Secretary of State added that the Cuban guards were also responsible for "internal intelligence" within the Maduro government, including "who was watching whom to make sure there was no betrayal from the inside."

The president said that "a number" of the Cuban guards responsible for Maduro's protection had died during the operation.

Trump also said that the Cuban economy, already battered by years of U.S. sanctions, was on the verge of collapse and would be exacerbated by the removal of Maduro, who has been providing subsidized oil to the Caribbean island nation.

"Cuba is collapsing," Trump said. "Cuba is going to collapse completely."

Trump told reporters on Saturday that the Cuban government was "very similar" to Venezuela.

"Cuba is going to be something we're going to be discussing down the road," Trump said. "Cuba is a failed state right now, a very serious failed state, and we want to help the people."

Cuban authorities called for rallies in support of the Venezuelan government and denounced the U.S. military operation in a statement that said, "All countries in the region must remain vigilant, because the threat looms over us all."

Rubio, a former Florida senator and a Cuban immigrant, has long argued that Cuba is a repressive dictatorship that oppresses its people.

"This is the Western Hemisphere. This is our backyard. We will not tolerate the Western Hemisphere becoming a base of operations for U.S. adversaries, competitors, and rivals," Rubio said.

Cubans like 55-year-old biochemistry lab technician Barbara Rodriguez were watching the events in Venezuela, expressing concern over what she called an "invasion of a sovereign country."

"It could happen in any country, even right here. We have always been a target," Rodriguez said, according to the Associated Press.

U.S. NNP=Reporter Sung Ku Hong / Special Correspondent for this newspaper NNP info@newsandpost.com