* Fuel cargo reached the port of Benghazi last week
* Could be part of an agreement to swap crude for products
* United States moving to approve trade with opposition
LONDON, April 28 (Reuters) - Fuel deliveries to Libya's rebel-held ports have restarted with trading house Vitol shipping at least one cargo of diesel to the port of Benghazi last week, industry sources said on Thursday.
A diesel cargo aboard the tanker Delos was loaded in Malta, where Vitol has floating storage capacity, and shipped across the Mediterranean Sea to eastern Libya just over a week ago, the sources said.
Ship tracking data provided by Marine Traffic shows the tanker reached Tobruk on April 17, and six days later, during which time there is no satellite information available, sailed from the port of Benghazi on April 23, heading back to Malta.
"The vessel loaded ship-to-ship out of Vitol's storage and moved to Tobruk over a week ago," one source said.
The fuel delivery was thought to be part of an agreement to swap crude oil in exchange for products.
A Vitol spokeswoman declined to comment on the delivery.
Vitol fixed a gasoline cargo to Benghazi earlier this month but it was not clear if it arrived.
The Delos has a capacity of around 43,000 tonnes, just over half the size of the crude oil cargo aboard the Equator, which Vitol lifted from the rebel-held east Libyan port of Marsa el Hariga three weeks ago.
When it passed through Suez earlier this month, a canal official said the tanker was carrying 80,000 tonnes, or the equivalent of 550,000 barrels of oil.
Trade in oil and products has ground to virtual standstill as companies avoid dealing with Libya for fear of infringing international sanctions.
But the United States this week took steps to boost aid to the Libyan opposition council and to approve oil exports made under its auspices, creating a loophole in U.S. sanctions that could mean millions of dollars in revenue for rebel coffers.
Reuters reported last week supplies have already reached west Libya which is under government control, as companies have taken advantage of a loophole in United Nations sanctions to deliver gasoline via Tunisia.
Trade in Libya remains a costly and risky business.
A tanker booked for Italian oil company Eni to carry crude to Italy from Gaddafi-held territory in Libya was forced to leave empty last week as government loyalists refused to allow the cargo to be loaded, trade sources said.
"They didn't want the crude to go, because they wouldn't have gotten any money for it," an industry source said on Wednesday, adding, "They could use it to refine into gasoline." (Reporting by Jessica Donati; editing by Emma Farge and Anthony Barker)