* Venezuela opposition wants executive order shielding Citgo
* $913 mln payment on PDVSA 2020 bond due in late October
* Colombia now U.S.-based refiner's largest source of foreign crude (New throughout, adds analyst comment, details on imports and exports)
By Luc Cohen
WASHINGTON, Oct 2 (Reuters) - U.S. President Donald Trump must act to prevent holders of Venezuelan state-run oil company PDVSA's bonds from taking control of U.S.-based Citgo Petroleum, the refiner's chairwoman said on Wednesday.
Venezuelan congress chief Juan Guaido this year took control of Citgo and appointed a board of directors after the United States and dozens of other countries recognized him as the nation's elected leader, calling President Nicolas Maduro's 2018 re-election a sham.
Guaido could lose control over Citgo, the country's top foreign asset, if Venezuela fails to make a $913 million payment on PDVSA's 2020 bond later this month. The bond is backed by a 50.1% stake in Citgo's parent and Guaido allies have been lobbying Trump for an executive order shielding Citgo from creditors.
"After the support that was given in order to save Citgo from Maduro, it seems to me contradictory that the same effort would not be made here to save Citgo from Maduro's bondholders," Chairwoman Luisa Palacios said at a conference organized by the Inter-American Dialogue.
The Trump administration so far has not taken steps to protect the company. Conservative groups have warned against further involvement, saying it would interfere with the free market.
Maduro, who Washington blames for Venezuela's economic collapse, cannot make the payment due to U.S. sanctions on PDVSA. The opposition made a $71 million interest payment earlier this year, but has not had access to funds for making the larger upcoming payment.
PDVSA did not respond to a request for comment.
Maduro, whose government remained current on the 2020 bond even as it has defaulted on billions of dollars in other debt, has accused the opposition of "stealing" Citgo.
Guaido has prioritized protecting Venezuela's overseas assets since invoking the constitution to assume an interim presidency in January.
Other creditors are circling, including Crystallex, a gold mining company whose Venezuela assets were expropriated a decade ago and aims to seize Citgo to collect on an arbitration award.
"This is a country that owes a lot of people a lot of money," said Risa Grais-Targow, Latin America director at consultancy Eurasia Group.
Sanctions on PDVSA have cut off Citgo's access to Venezuelan crude. In 2018, Citgo imported around 176,000 barrels per day (bpd) of Venezuelan oil, about 24% of that year's supplies, according to Palacios' presentation.
As a result, it boosted U.S. crude purchases to 308,000 bpd in the first half, and increased imports from other countries. Colombia now is Citgo's largest foreign crude supplier, ahead of Canada, Mexico, Trinidad & Tobago and Brazil, Palacios said.
Citgo's product exports to Venezuela also were halted by sanctions. "We lost an important market," Palacios said, adding that Citgo was prepared to resume fuel shipments to help with the country's reconstruction under a new government. (Reporting by Luc Cohen; editing by David Evans and David Gregorio)