Secretary of State Marco Rubio said on Thursday that there would be “consequences” if Venezuela used forceful actions in asserting claims to resource-rich territories that are under the control of neighboring Guyana.
Mr. Rubio said at a news conference in Georgetown, the Guyanese capital, that his government would steadfastly oppose “the regional threats based on illegitimate territorial claims by a narco-trafficking regime.”
“There will be consequences for adventurism,” he said as he stood on a stage with Irfaan Ali, the president of Guyana, a small country along the northern coast of South America. “There will be consequences for aggressive actions, and that’s why our partnership in that regard will be important.”
In recent years, Venezuela has intensified claims to the Essequibo region that makes up about two-thirds of Guyana’s territory and includes the oil-rich offshore waters where oil production led by ExxonMobil is occurring.
Mr. Rubio said he would not specify what the Trump administration would be prepared to do, but pointed out the power and size of the U.S. Navy, implying the United States would take military action.
“I’m very pleased at the reassurance of the U.S. at ensuring the safeguard of our territorial integrity and sovereignty,” Mr. Ali said.
On March 1, Mr. Ali denounced what he called an illegal incursion by a Venezuelan naval vessel into waters near where Exxon is leading a group of companies in extraction.
“This is a serious development concerning our nation’s maritime territory,” he said on television. “We will not tolerate threats to territorial integrity.”
The U.S. State Department expressed support for Guyana and warned Venezuela’s government in a social media post against “further provocation.”
The vice president of Venezuela, Delcy Rodríguez, said at the time that Mr. Ali was telling “baldfaced lies” and that Exxon’s oil-producing operations were illegal.
Exxon discovered the oil reserves in 2015. The Essequibo region is also coveted for its gold, bauxite, diamond, uranium, manganese and other minerals.
On Monday, President Trump said he would impose a 25 percent tariff on any country that buys oil from Venezuela.
Mr. Rubio’s stop in Guyana was the first of two on Thursday during a three-nation tour of the Caribbean and South America. He had been in Jamaica, where he met with the prime minister, and later on Thursday was traveling to Suriname.
Both Guyana and Suriname are oil-rich countries, and Mr. Trump and Mr. Rubio have stressed the U.S. need for energy security, including through greater fossil fuel production despite concerns among scientists about a deepening climate crisis.
In January, Mr. Trump withdrew the United States from the Paris Agreement on climate change. He did the same in his first term, but the United States re-entered the pact under President Joseph R. Biden Jr.
On Tuesday, the day before Mr. Rubio left for his trip, the Trump administration’s special envoy for Latin America, Maurcio Claver-Clarone, noted that Guyana was on the verge of becoming the largest per capita oil producer in the world, surpassing Qatar and Kuwait.
“It’s seen as some of the greatest offshore opportunities in the world,’’ he told reporters. “The security of Guyana is a key priority for us in the same way that we have been working with countries in the Gulf States to ensure the security cooperation from the regional threats there.”
“We’ve seen the threats from Venezuela,’’ he added. “We’ve seen the approaches towards Exxon facilities. Obviously, that’s unacceptable.’’
For many years, the U.S. government has maintained a hostile stance toward the government of President Nicolás Maduro in Venezuela. The first Trump administration imposed broad sanctions on the country and tried to support an opposition leader, Juan Guaidó, in his bid to unseat Mr. Maduro.
At the time, Mr. Rubio, then a U.S. senator representing Florida, promoted policies aimed at deposing Mr. Maduro in favor of Mr. Guaidó.
After a disputed presidential election last year that Mr. Maduro is widely believed to have stolen, Mr. Biden recognized the opposition candidate as the legitimate winner.
A reporter from Guyana pressed Mr. Rubio on what the United States would do if the Venezuelan military were to strike Guyana or ExxonMobil.
“It would be a very bad day for the Venezuelan regime if they were ever to attack Guyana or attack ExxonMobil,” Mr. Rubio said. “It would be a very bad day, a very bad week for them.”
An audience of Guyanese officials clapped.