(Bloomberg) -- Mexico and Cuba are trying to find two small vessels that were delivering aid to the island as part of growing solidarity missions in the face of heightened US pressure on the government in Havana.

Mexican President Claudia Sheinbaum told reporters on Friday that authorities were searching for two sailing boats that left Mexico a week ago to make the 200-mile (322-kilometer) journey. Cuban President Miguel Díaz-Canel said earlier on X that his nation was “doing everything possible to find and save our brothers in arms.”

The US Coast Guard said it was notified by Mexican authorities about the two missing boats on Thursday. The agency hasn’t yet been asked to assist in the search, though it stands ready to do so if requested, according to an emailed statement.

Washington has been turning the screws on Cuba in hopes of toppling the 67-year-old communist regime. Since Donald Trump ordered the capture of the island’s principal ally in Venezuela on Jan. 3, the US has imposed a near-total blockade on fuel deliveries to the Caribbean nation, exacerbating blackouts and economic decline.

Díaz-Canel, in a rare press conference, confirmed for the first time on March 13 that talks are talking place with US officials. He also the island hadn’t received a fuel shipment in more than three months.

Even so, Mexico and others have been sending food, medicine and other forms of aid. Last week, a group of progressive activists, including former UK Labor Leader Jeremy Corbyn, former Spanish politician Pablo Iglesias, and US political streamer Hasan Piker, delivered about 14 tons of aid as part of the “Our America Convoy.”

Cuba’s long-time ally in Moscow, however, appears poised to test the US blockade.

The Anatoly Kolodkin departed from Russia on March 8 carrying an estimated 730,000 barrels of crude, according to ship-tracking data compiled by Bloomberg. The Russian-flagged tanker broadcast its destination as “Atlantic for order,” but analysts suspect it intends to dock at the Cuban port of Matanzas.

The Sea Horse, another tanker carrying Russian fuel that was initially bound for the island, changed course earlier this month. It rerouted to Venezuela after the Treasury Department clarified that Cuba remains ineligible to receive Russian oil, despite relaxing sanctions on other countries buying Moscow’s crude in an effort to tame surging oil prices amid the US-Israeli war in Iran.

--With assistance from Ella Feldman.

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