WASHINGTON (Reuters) - The United States imposed sanctions on Tuesday against Venezuela's state-run gold mining company Minerven and its president, Adrian Perdomo, accusing them of illicit operations and propping up the government of President Nicolas Maduro.

The announcement comes days after Uganda said it was investigating its biggest gold refinery for importing Venezuelan gold. Washington has imposed half a dozen rounds of sanctions against Maduro and senior Venezuelan officials as it tries to choke off funding to the government. It has warned gold traders not to deal in Venezuelan gold or oil.

"Treasury is targeting gold processor Minerven and its president for propping up the inner circle of the corrupt Maduro regime," U.S. Treasury Secretary Steven Mnuchin said in a statement.

Maduro is under intense pressure to step down amid a deep economic crisis in Venezuela and as the government faces widespread international condemnation after he was re-elected last year in a vote that has been seen as fraudulent.

"We will aggressively pursue those involved with Maduro’s reckless illicit gold trade which is contributing to this financial, humanitarian, and environmental crisis," Mnuchin said.

Venezuela's opposition leader Juan Guaido, who invoked the constitution to assume the interim presidency in January saying Maduro's re-election was not legitimate, has sought to prevent the gold sales, arguing that Maduro uses the proceeds to try to stay solvent.

Most Western countries have backed Guaido as Venezuela's head of state.

The U.S. Treasury said Minerven - the abbreviated name for Compania General de Mineria de Venezuela - bought gold from miners and converted it to bars, after which it was transported by the military to air bases and stored at the central bank.

Venezuela's opposition has accused Maduro of selling the country's gold holdings to Turkey and the United Arab Emirates without approval by the opposition-led National Assembly.

The U.S. Treasury accused Maduro's government of maintaining the support of the military by giving military officers "liberal access to the mines."

"This furthers Maduro’s ability to maintain power over the military, as its desire to protect this illicit income reinforces the military’s staunch loyalty to Maduro," the Treasury said.

(Reporting by Lesley Wroughton, Susan Heavey and Doina Chiacu; Editing by Bernadette Baum)