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HOUSTON, April 14 (Reuters) - A vessel chartered by Chevron CVX.N carrying some 500,000 barrels of Venezuelan oil is about to complete the discharge of the cargo at a Venezuelan port, according to shipping data and a source, following state company PDVSA's order to return the crude amid payment uncertainty related to U.S. sanctions.

At least nine tankers Chevron had chartered to carry Venezuelan crude to the U.S. in coming weeks as part of the wind down of its U.S. license through May 27 are now stalled in the Caribbean Sea waiting for directions after PDVSA last week ordered two cargoes to be returned and canceled loading permits to others, cutting the deadline short.

The Bahamas-flagged vessel, Carina Voyager, managed by a Chevron unit, on Saturday began discharging at PDVSA's Jose port the cargo it originally intended to export, LSEG shipping data showed.

The tanker is scheduled to finish the oil return on Monday, a source close to PDVSA's operations said, adding that a second cargo to be returned by Chevron, on Marshall Islands-flagged tanker Dubai Attraction, will discharge some 300,000 barrels of Boscan heavy crude at PDVSA's Amuay terminal in coming days after the U.S. company completes a port inspection.

Venezuela's Vice President Delcy Rodriguez, who is also the OPEC country's oil minister, on Friday blamed the U.S. measures for the issue, saying they prevented Chevron from paying for the oil.

"Because of the economic war initiated by the U.S. government against oil companies, Chevron has returned cargoes of crude to PDVSA," Rodriguez said on social media. "This crude is being sold on international markets."

Chevron did not immediately reply to a request for comment.

A license issued in 2022 by the U.S. Treasury Department for Chevron to operate in Venezuela was revoked in March by President Donald Trump's administration, granting the May deadline to wind down operations and oil exports.

The same deadline was granted to other partners of PDVSA, including Eni ENI.MI, Repsol REP.MC, Maurel & Prom MAUP.PA and Reliance Industries RELI.NS, to wind down oil cargoes bound for Europe and Asia.

(Reporting by Reuters staff, additional reporting by Sheila Dang; Editing by Sharon Singleton)

((marianna.parraga@thomsonreuters.com; +1 713 371 7559; Reuters Messaging: @mariannaparraga))