Mining company Crystallex International said on Thursday Venezuela failed to honor a settlement and urged a federal judge to allow it to seize control of U.S. refiner Citgo Petroleum, which is owned by the country's state oil company.

Oil workers conduct a drill in a petroleum well in Lagunillas at the east coast of Lake Maracaibo near Maracaibo City in Venezuela.

Canada-based Crystallex won a 2016 international arbitration award of $1.2 billion against Venezuela, which has refused to pay. The company had been trying to collect by seizing shares of Citgo's U.S. parent company, which is owned by Venezuelan state oil company PDVSA.

Last month Crystallex said it settled with cash-strapped Venezuela, but the company's lawyer said that deal fell through. "They said they'd make a payment to us and didn't," Robert Weigel, a lawyer for Crystallex, told the court Thursday.

Crystallex's lawyers told U.S. Judge Leonard Stark in Wilmington, Delaware, they had an "avalanche of evidence" that proved PDVSA and Venezuela were one and the same, including official PDVSA tweets with the hashtag #PDVSAesVenezuela, Spanish for "PDVSA is Venezuela."

As a result, they were seeking to attach, or seize, PDVSA's shares in PDV Holding Inc, Citgo's Delaware-incorporated parent.

If Crystallex succeeds, the case could open the way for more than a dozen companies to pursue Citgo to collect on arbitration claims over assets that were nationalized under Venezuela's late socialist leader Hugo Chavez.

PDVSA's lawyer argued on Thursday that Crystallex could not pursue the state oil company's assets because PDVSA was not a party to the arbitration.