HOUSTON (Reuters) -A U.S. judge allowed an affiliate of hedge fund Elliott Investment Management on Thursday to move towards completing its offer for Venezuela-owned Citgo Petroleum's parent through a court-ordered auction of shares, while restricting rival bidder Gold Reserve ( GDRZF ) from doing the same.

This followed a separate judge in another U.S. court upholding the validity of Venezuelan state oil company PDVSA's 2020 bonds on Thursday.

Delaware Judge Leonard Stark instructed a court officer overseeing the auction of shares to terminate a stock purchase agreement (SPA) with a Gold Reserve ( GDRZF ) subsidiary and sign a new one with Elliott's affiliate Amber Energy, Gold Reserve ( GDRZF ) said in a release.

That came at the end of a 4-day sale hearing, where some of the 15 Venezuela-linked creditors lining up to cash proceeds from the auction for Citgo's parent asked him to move the auction forward by granting key agreements with frontrunner bidder Amber.

The creditors have resorted to U.S. courts seeking compensation for debt defaults and expropriations in Venezuela.

An SPA is a legally binding contract that outlines the terms for the sale and transfer of a company's shares. In an auction of shares, the SPA is a key step to allow a frontrunner to secure financial commitments and complete regulatory filings for the shares' transfer.

Gold Reserve's ( GDRZF ) unit Dalinar Energy and Amber have been competing neck and neck in recent months for Citgo's parent, PDV Holding.

Because Amber's $5.9 billion offer includes a separate $2.1 billion agreement to pay holders of a defaulted Venezuelan bond, the Delaware court has recommended it as the best bid. Dalinar's offer did not include a similar provision.

Judge Stark has not made a final decision on the winner. But he also denied on Thursday a motion by Gold Reserve ( GDRZF ) to disqualify Amber's bid, the miner said in a statement.

"The decision was delivered orally from the bench. Gold Reserve ( GDRZF ) expects a written opinion and order to be issued shortly," it added.

A New York judge on Thursday confirmed the validity of defaulted Venezuelan bonds collateralized with Citgo equity, supporting the holders' claim and boosting Amber's bid.

(Reporting by Marianna Parraga; Editing by Jacqueline Wong and Muralikumar Anantharaman)