The world's largest publicly traded energy company was still on the list in early February but has since been removed, while Syrian General Oil has been added as a pre-qualified bidder.

"The Final Tender Protocol and the definitive model Contract have been issued to all prequalified companies," Abdul Mahdy Al-Ameedi, director general of the Petroleum Contracts and Licensing Directorate (PCLD), said in a statement.

"We are looking forward to welcoming all participating companies in Baghdad."

Exxon has angered Baghdad by signing an exploration deal with the Kurdistan Regional Government (KRG), which the central government considers illegal.

Iraq's oil and gas fields have suffered from decades of neglect because of war and economic sanctions.

The bidding for 12 new exploration blocks, which has been repeatedly delayed but is now due to be held May 30-31, is expected to add 29 trillion cubic feet of gas and 10 billion barrels of oil to Iraqi reserves.

Iraq improved the terms of the blocks in February after complaints by several prospective bidders that the deals were unattractive.

The upcoming auction will focus mainly on gas exploration rights, and the blocks are mostly in remote parts of western and central Iraq, making them riskier investments since the sites are harder to protect against insurgent attacks.

Companies will be able to extract gas discovered in the blocks immediately, but the Iraqi government has retained the option to prevent companies from extracting oil in exchange for paying them compensation.

Exxon, which has a large and growing portfolio of conventional and unconventional gas assets around the world, many in far less challenging environments than Iraq, was unavailable for immediate comment.

(Reporting by Daniel Fineren; Editing by Jason Neely and Alison Birrane)

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