Washington DC - President Donald Trump claimed Mexico is on the verge of ceasing all shipments of oil to Cuba, despite contrary claims made repeatedly by Mexican President Claudia Sheinbaum.

"It's a failed nation. Mexico is going to cease sending them oil," Trump told reporters in the Oval Office on Monday when asked about Cuba.

Cuba is already struggling to find a reliable source of oil, since the Trump administration cut off its access to Venezuelan shipments after the abduction of President Nicolás Maduro in early January.

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

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As a result, the Mexican government has been reluctant to cut supplies, with Sheinbaum last week warning of a "far-reaching humanitarian crisis directly affecting hospitals, food supplies, and other basic services."

On Thursday, Trump signed an executive order directing his administration to impose additional tariffs on any countries that send oil to the beleaguered Caribbean nation.

The decree effectively forces Cuba's partners to choose between trade with the world's largest economy or with the island of 11 million people.

Sheinbaum, who has vowed solidarity with Cuba amid increasing pressure from the US, responded to Trump's comments on Monday by pledging humanitarian aid to Cuba.

"We never discussed with President Trump the issue of oil with Cuba," Sheinbaum said at an event on Sunday, referencing a call with Trump last week. "We are exploring all diplomatic avenues."

"This week we are planning humanitarian aid to Cuba," she confirmed. "The Mexican military will be sending food and other essential products while we diplomatically resolve the issue of sending oil."