A Russian tanker carrying 730,000 barrels of crude oil has reached Cuba, marking the first delivery since the US imposed a de facto fuel blockade in January.

Despite earlier threats, US President Donald Trump now says he has "no problem" with countries sending oil to the crisis-hit island, where severe shortages have caused repeated nationwide blackouts.

Cecile Shea, an expert on security and diplomacy at the Chicago Council on Global Affairs, analyzes what the delivery means for the US's blockade strategy for Cuba.