HOUSTON, June 25 (Reuters) - Venezuela's state oil

company PDVSA has begun using tankers that navigate off radar to

supply its closest political ally, Cuba, as a fleet of

state-owned vessels that have historically covered the route

dwindles, according to documents and ship monitoring services.

Cuba and its main oil supplier, Venezuela, for over a decade

had exclusively used their own tankers to navigate between the

two countries.

Delayed maintenance, however, has taken some ships out of

service and the emergence of Mexico as a new supplier to Cuba

using some of the same vessels have the two revamping routes to

get desperately needed crude oil and fuel to the island.

A large portion of tanker fleets owned by Venezuela and Cuba

are under U.S. sanctions, which also limits their travel.

Operated by third parties, dark fleet vessels often lack western

insurance and send false location signals to disguise their

movement.

PDVSA in June began co-loading crude and fuel oil cargoes

that deliver a portion in Cuban waters, and from there depart to

destinations in Asia to discharge the remaining volume,

according to company shipping documents.

The vessels spoof their signal, making them look elsewhere

in the Caribbean while they are discharging in Cuba, often by

ship-to-ship transfers, according to monitoring service

TankerTrackers.com and a satellite photo by Planet Labs seen by

Reuters.

One of the vessels, the Panama-flagged Neptune 6, was last

week near Cuba's Nipe Bay transferring Venezuelan heavy crude

and fuel oil to Cuba-flagged vessel Esperanza, according to the

documents and photo, analyzed by TankerTrackers.com. The ship's

transponder is signaling a location north of Curacao since late

May, according to LSEG data.

PDVSA and the foreign affairs ministries of Venezuela

and Cuba did not provide comment. It was not immediately clear

if the use of third-party vessels to supply Cuba is temporary.

IN NEED OF BARRELS

The extra vessels could help boost Venezuela's oil supply to

Cuba, which so far this year is at 27,000 barrels per day (bpd),

compared with 51,500 bpd in the same period of 2023.

The covert help comes as demand for electricity produced

by oil-fired plants soars during sultry Cuban summers.

Blackouts that were occasional in Cuba have become routine

as imported supplies are limited and logistical issues

complicate domestic fuel distribution to its aging power plants.

Cuban energy officials also have said workers are tuning up

and providing maintenance to power generating plants ahead of

the high-demand summer season, and hope the coming months will

see fewer blackouts.

Cuba has not been able to fully recover its oil storage

capacity since a devastating fire destroyed a portion of the

island's largest oil terminal, Matanzas. The lack of tanks

forces suppliers to transfer cargoes to other ships used for

floating storage by Cuba.

In May, Mexico's state company Pemex resumed oil shipments

to Cuba after a three-month pause in the same vessels used to

ship oil from Venezuela, Reuters reported.