US President Donald Trump said on Monday that Mexico would stop sending oil to Cuba ‌as he ramped up a pressure campaign on the Caribbean nation.

“Mexico is gonna ‍cease sending them oil,” Trump told reporters in the White House Oval Office. He did not elaborate on why he believed this to be the case.

Mexican authorities did not immediately respond to a request for comment.

Mexico is the single-largest supplier ⁠of oil to Cuba, which regularly suffers from energy shortages and mass blackouts. Cuba relies heavily on fuel imports of refined products to meet its demand for electricity generation, petrol, and aviation fuel.

US sanctions and a deep economic crisis have prevented the Communist government from buying enough fuel for years, forcing it to ‍depend on a small group of allies. Reuters has reported that the Mexican government is reviewing whether to ‍keep sending oil to Cuba, as it worries that Mexico could face reprisals from the United States over its policy to do so.

President Claudia Sheinbaum’s administration said ‌on Sunday it would seek to ship oil to Cuba for humanitarian reasons, “without seeking confrontation”. But they also ‍said aid would consist of “other” products for the coming week.