HOUSTON, Oct 26 (Reuters) - A 2.1 million-barrel cargo of Iranian condensate, the most recent delivery from a swap pact between the Middle Eastern nation and Venezuela, is expected to begin discharging on Wednesday at a PDVSA port, a document from the state-run firm showed.

The U.S.-sanctioned state oil companies from both countries, PDVSA and National Iranian Oil Company (NIOC), last month agreed to a contract https://www.reuters.com/article/venezuela-iran-oil-idCNL1N2QM1HJ, in effect for six months in its first phase, to exchange Iranian condensate for Venezuelan heavy crude.

The first cargo belonging to the swap set sail from Venezuela in September on Iranian tanker Felicity. Iran then supplied PDVSA with a first cargo of condensate on tanker Dino I, which sailed back last week carrying Venezuelan crude.

The second cargo of Iranian condensate arrived in Venezuelan waters on Monday on Iran-flagged tanker Dorena, according to the document, which did not detail the name of the supplier.

Even under Washington's watchful gaze, Iran and Venezuela have since last year strengthened cooperation. President Nicolas Maduro's administration has received food, refinery parts, condensate and fuel from Iran; while sending crude oil and other commodities to its ally.

PDVSA and NIOC did not immediately reply to requests for comment.

The swap deal could be a breach of U.S. sanctions on both nations, according to a Treasury Department email to Reuters in September, which cited U.S. government orders that establish the punitive measures.

The condensate is expected to help PDVSA free up medium and light crudes to reanimate domestic refining, while resuming crude output at many oilfields that had been shut due to an acute lack of material to dilute the nation's extra heavy oil.

(Reporting by Marianna Parraga; Editing by Gary McWilliams and Marguerita Choy)