Venezuela's falling crude output and financial woes have left it struggling to maintain a 15-year-old oil assistance program to its closest ally, Cuba.
State-run oil firm PDVSA has slashed its exports to Cuba this year, according to the company's internal trade data, seen exclusively by Reuters.
The shift signals an unraveling of the oil diplomacy pioneered by Venezuela's late socialist leader Hugo Chavez and helps explain why Cuba, which generates electricity from fuels, recently ordered some joint ventures and state-owned firms to reduce power usage.
It also comes as Cuba improves its relations with the United States after decades of standoff and a US economic embargo while Venezuela, mired in triple-digit inflation and acute product shortages, is in a prolonged standoff with Washington.
Cuba, long reliant on Venezuela as its top energy supplier, has received some 53,500 barrels per day of crude from PDVSA this year, a 40% decline from the first half of 2015, according to the company's data.
When it was flush with cash from oil exports, Venezuela's government won political support in Latin America and the Caribbean by sending oil on advantageous terms to allies.
Cuba, which receives some 4% of Venezuela's total oil exports, has been the biggest beneficiary of the program and until this year was spared the fallout from PDVSA's growing cash flow problems, which already undermined oil supplies to Uruguay, Jamaica, Dominican Republic and Curacao.
Venezuela has partially offset the smaller crude shipments to Cuba by boosting exports of refined products such as fuel oil, diesel and liquefied petroleum gas.
But overall shipments to Cuba, including both crude and products, still declined 19.5% to 83,130 bpd in the first half of this year.
It is unclear if Cuba is looking to secure new sources of supply amid the shortfalls. The barter arrangement for Venezuelan oil has been a huge boost to Cuba's economy and it would have to pay much more in the open market.
Venezuela has the world's largest crude reserves though output has declined in recent years because of underinvestment. Given a slump in oil prices and a mounting economic crisis at home, PDVSA is straining to keep up investment and production.
Numerous oil analysts believe the OPEC country's oil output this year will fall to its lowest level since a devastating strike at PDVSA in 2002 and 2003. PDVSA said this month its sales revenue fell more than 45% in 2015.
