Mexico City, Mexico - Mexico was using all available "diplomatic channels" to ensure the resumption of crude shipments to struggling Cuba, which Washington has threatened to cut off from life-giving oil, President Claudia Sheinbaum said Tuesday.

Cuba, in the grips of an economic crisis, has long relied on oil supplies from Venezuela, whose leader was ousted in a deadly US military operation last month.

US President Donald Trump subsequently claimed control of Venezuelan oil, vowed to starve Cuba of the commodity, and threatened tariffs on any other nation stepping in to help US-sanctioned Havana.

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Sheinbaum has been reluctant to cut supplies as she warned of a humanitarian crisis in Cuba, but is also keen to not put her own country "at risk in terms of tariffs."

On Monday, Trump said Mexico would stop sending oil to Cuba, which he described as "a failed nation."

The end of Mexican supplies would significantly deepen what is already Cuba's most serious economic crisis since the 1991 collapse of the Soviet Union.

On Tuesday, Sheinbaum said Mexico would send humanitarian aid to Cuba this week and is seeking an agreement with Washington that would allow it to also send oil.

Sheinbaum, who previously refused to confirm media reports that Mexico had already stopped providing oil to Cuba, was asked Tuesday when shipments would resume.

"We're looking at the scope of" Trump's threatened tariffs "and we're using all diplomatic channels. There is still no agreement on this," she replied.

The Cuban economy has sputtered along in recent years thanks to Venezuelan oil in exchange for Cuba sending doctors, teachers, and other professionals.