HOUSTON, Aug 23 (Reuters) - A U.S. federal court officer

overseeing an auction of shares in the parent of Venezuela-owned

refiner Citgo Petroleum on Friday requested a new extension to

evaluate bids and select a winner of the bidding round,

according to a court filing.

A complex bidding system in an unprecedented court case to

pay up to $21.3 billion in debts from expropriations and debt

defaults in Venezuela has repeatedly created delays. The auction

is expected to see an ownership change of the seventh-largest

U.S. refiner.

The proposed extension, the third requested so far this

year, would give Delaware court officer Robert Pincus until

Sept. 16 to choose and recommend a winner. Parties would have 21

days after that to file any objections, with the final sales

hearing to be held on Nov. 7, the court document said.

The two leading bidders in the auction are refiner CVR

Energy ( CVI ), backed by billionaire investor Carl Icahn, and

an investment group led by miner Gold Reserve ( GDRZF ), sources

told Reuters last month.

The long-running case, first introduced in 2017, has broken

new ground in its treatment of international arbitration awards

and foreign sovereign immunity issues. The court found Citgo's

parent PDV Holding liable for Venezuela's debts.