July 19 (Reuters) - The U.S. on Wednesday approved a three-month extension to a license protecting Citgo Petroleum from creditors seeking to seize the oil refiner's assets.

The document comes as a negotiation team representing Venezuela progresses in talks with bondholders and creditors with arbitration awards from expropriation claims, a move to avoid a breakup of Venezuela's most important foreign asset.

Creditors have flocked to U.S. courts to press claims on over $20 billion, almost double the value of Citgo Petroleum, which operates an 807,000-barrel-per-day oil refining network in the United States.

Below is a list of the companies and investors who have sought to attach claims to a stake in Citgo, the Houston-based subsidiary of state oil company PDVSA, and a summary of where their cases stand.

PDVSA 2020 BONDHOLDERS

PDVSA in 2019 defaulted on bonds maturing in 2020, which were backed by a 50.1% stake in Delaware-registered Citgo Holding, the oil refiner's immediate parent company. The bondholders in 2020 won a U.S. court judgment allowing them to collect $1.9 billion in defaulted principal and interest payments.

PDVSA - whose U.S. assets are controlled by Venezuela's opposition due to sanctions on President Nicolas Maduro's socialist government - sued in Manhattan federal court to invalidate the bonds, arguing they were never approved by Venezuela's congress.

PDVSA submitted written arguments on March 27, and bondholders followed in June. It is not clear when the court will rule on the bonds.

On June 30, investment fund VR Global Partners LP - which holds $30 million worth of the bonds - sued PDVSA in Manhattan federal court, alleging the company fraudulently induced investors to purchase the bonds even though it privately believed they were invalid under Venezuelan law.

CRYSTALLEX

Canadian gold miner Crystallex is seeking to attach shares in PDV Holding, another Delaware-registered PDVSA subsidiary, to collect $970 million outstanding from a $1.4 billion arbitration award for Venezuela's expropriation of the company's Las Cristinas mining project in the South American country.

U.S. District Court Judge Leonard Stark has granted Crystallex permission to seize the shares, but existing sanctions on Venezuela bar any sale or transfer. The U.S. in May told the court it would look favorably on the proposed auction of shares.

Stark could approve bidding and sale procedures this month. Under the proposed auction, PDV Holding shares would be sold to the highest bidder with proceeds used to compensate Crystallex and possibly others.

CONOCOPHILLIPS

Stark has said he will grant ConocoPhillips permission to seize PDV Holding shares once sanctions allow for it. The oil company is seeking to collect on $1.29 billion outstanding from a $2 billion arbitration award over PDVSA's early termination of its Hamaca and Petrozuata projects in Venezuela.

The company also has an $8.5 billion award from the World Bank's ICSID dispute settlement body against Venezuela's government over those same projects. Venezuela introduced a request for the judgment to be annulled, which is pending.

Besides Crystallex and Conoco, Stark also has recognized a claim of about $163 million from Siemens Energy and a $246 million claim from Red Tree Investments, which could receive auction proceeds.

OTHER AWARD HOLDERS

Several other companies have obtained judgments in U.S. courts recognizing arbitration awards they have won against Venezuela for asset expropriations in the country or unpaid bills.

A U.S. court of appeals in July rejected Venezuela's bid to prevent O-I Glass, Huntington Ingalls Industries, ACL1/ACL2/LDO Investments, Koch Minerals and Nitrogen, and mining firms Rusoro Mining and Gold Reserve from joining the proposed auction of shares in Citgo Petroleum's parent.

The decision allows the six firms to move ahead with about $3 billion in combined claims against PDVSA in Delaware.

OTHER BONDHOLDERS

Venezuela's government and PDVSA have also defaulted on billions of dollars' worth of bonds which, unlike the PDVSA 2020 bonds, are not secured by shares in Citgo.

Several holders of those bonds have also won judgments in U.S. courts recognizing they are owed money.

(Reporting by Luc Cohen in New York and Marianna Parraga and Gary McWilliams in Houston Editing by Matthew Lewis)