HOUSTON (Reuters) - The board of Citgo Petroleum appointed by Venezuela’s congress chief was properly seated, a U.S. court ruled, dealing a blow to contested Venezuelan President Nicolas Maduro’s efforts to retake control of the Texas-based refiner.

FILE PHOTO: The Citgo Petroleum Corporation headquarters are pictured in Houston, Texas, U.S., February 19, 2019. REUTERS/Loren Elliott/File Photo

Venezuelan congress chief Juan Guaido’s recognition by the Trump administration as the South American country’s legitimate leader makes his Citgo appointments valid, Delaware Chancery Court Vice Chancellor Kathaleen McCormick ruled on Friday.

The ruling provides U.S. court backing for Guaido as the country’s official leader with power to name directors of Citgo and its parent, Petroleos de Venezuela [PDVSA.UL] (PDVSA). However, McCormick delayed the ruling for 10 days to give Maduro’s lawyers time to challenge the process used to confirm the appointments.

“We are grateful that the court has rejected the Maduro regime’s efforts to use the U.S. judiciary to advance their anti-democratic objectives,” Citgo said in a statement.

Quinn Smith, an attorney who represents the Maduro-appointed board, said the group is reviewing the judge’s opinion and considering its next steps. Neither PDVSA nor the Venezuelan oil ministry immediately responded to requests for comment.

Citgo, Venezuela’s most important foreign asset, has been caught in a tug-of-war as President Donald Trump’s government has tried to use the firm as leverage to topple Maduro. Sanctions have barred Citgo from buying Venezuelan crude or paying it dividends.

Judge McCormick said the court “accepts as binding the U.S. President’s recognition of the Guaido government and assumes the validity of the Guaido government’s appointments to the PDVSA board.” If lawyers for Maduro cannot show the Guaido board was improperly appointed, she could issue an order confirming its members by Aug. 16.

Her ruling set a high hurdle for Maduro’s lawyers to challenge the directors. McCormick wrote the court generally accepts director seatings, and noted the Maduro board’s lawyers “do not appear to contest the authority” of the officials who authorized the appointments.

The Maduro-group could challenge the decision. Smith declined to comment on whether it would pursue an appeal.

In February, the Guaido-led congress appointed an ad-hoc PDVSA board with rights to nominate directors for U.S. units PDV Holding, Citgo Holding and Citgo Petroleum. However, Maduro retains the support of the Venezuelan military and still controls PDVSA and most state functions.

The Trump administration in January imposed sanctions on Venezuela and PDVSA designed to curb its oil revenue to pressure Maduro to step aside. Since then, its shipments have declined about 40%.