Cuban diplomats say Havana is ready to talk to Washington but certain things have yet to be discussed, including the constitution and its socialist government.

A Cuban diplomat said Cuba and the United States are communicating, but with U.S. President Donald Trump stepping in, those exchanges have not yet evolved into a formal “dialogue.” Pressure on Havana.

Cuban Deputy Foreign Minister Carlos Fernandez de Cosio told Reuters on Monday that the U.S. government was aware that Cuba was “ready for serious, meaningful and responsible dialogue.”

De Cosio’s statement is the first time Havana has suggested it is engaging with Washington, even in a limited way, as tensions have risen in recent weeks over Trump’s threats to the Cuban government after U.S. troops kidnapped it. Venezuelan leader Nicolás Maduroa long-time ally of Cuba.

“We exchanged information, we established an embassy, ​​we communicated, but we cannot say we have had a dialogue,” DeCosio said.

“If we can have a conversation, maybe that will lead to negotiations,” DeCosio said in a separate interview with The Associated Press.

The deputy minister also stressed that certain issues are off-limits for Cuba, including the country’s constitution, economy and socialist system of government.

On Sunday, Trump said the United States had begun talks with “the most senior people in Cuba.”

“I think we’re going to make a deal with Cuba,” Trump told reporters at his Mar-a-Lago resort in Florida.

Days earlier, Trump called Cuba an “unusual and extraordinary threat” to U.S. national security in an executive order and Warn other countries If they supply oil to Cuba, he will impose more tariffs on it.

Trump renewed his threat to Havana on Monday, announcing at the White House that Mexico “will stop” sending oil to Cuba, a move that could starve the country of its energy needs.

Mexico has yet to comment on Trump’s latest statement largest oil supplier To Cuba.

Mexico has repeatedly said it will not stop oil shipments to Cuba for humanitarian reasons, but it is also concerned that its policy could lead to retaliation from Trump.

The United States has moved in recent weeks to block all oil from entering Cuba, including from Cuba’s ally Venezuela, pushing up food and transport prices and causing severe fuel shortages and lengthy power outages even in the capital, Havana.

In response to Trump’s threats about oil supplies, Cuba’s DeCosio said the move would ultimately be counterproductive.

“The United States… is trying to force every country in the world not to provide fuel to Cuba. Is this sustainable in the long term?” DeCosio told Reuters.

The United States has imposed tough sanctions on Cuba for decades, but the island’s severe economic crisis and mounting pressure from the Trump administration have recently brought the conflict to a fever pitch.