Petroleos de Venezuela SA has sought preliminary purchase offers for its American unit Citgo Petroleum and a sale could help the oil and gas firm rake in about $10bn.

Citgo's US assets, the core of which are three refineries in Illinois, Louisiana and Texas with a combined capacity of 749,000 barrels per day (bpd), could fetch between $8bn (£5bn, €6.2bn) and $10bn, Reuters reported.

Bidders can present offers for individual assets, which include refineries, terminals, storage and wholesale operations. They have until end September to table preliminary offers.

Investment bank Lazard, which is managing the Citgo sale process, on behalf of PDVSA, has dashed out offering materials to potential buyers.

Likely buyers could include HollyFrontier, PBF Energy, Tesoro, Valero Energy and Western Refining, unnamed sources told the news agency.

The assets being offered, through Lazard, command annual earnings before interest, taxes, depreciation and amortization (EBITDA) of nearly $1.5bn.

Pursued by Reuters, PDVSA said it was "looking into the matter", while Lazard could not be reached for comment.

Citgo has 48 petroleum product terminals, three fully owned pipelines and six jointly owned pipelines in the US. Its brand is also carried on thousands of independently owned gas stations.

PDVSA accounts for 97% of Venezuela's dollar earnings.

Venezuela is offloading Citgo in part due to a cash crunch, triggered after Caracas repaid debts to Beijing with oil instead of selling crude to generate revenue, analysts have said.

Caracas has, however, denied that a cashflow problem exists.