(Corrects to 'Nicolas' from 'Nicholas' paragraph 5)
HOUSTON, July 7 (Reuters) - Venezuelan crude exports to the United States fell to 491,340 barrels per day (bpd) in June, the lowest monthly level since early 2003, because of fewer sales by state-run PDVSA to its unit Citgo Petroleum, according to Thomson Reuters Trade Flows data.
Venezuela's crude production has sharply decreased since 2012 amid a lack of investment and payment delays to oil service companies, affecting exports to PDVSA's customers, including those in the United States.
PDVSA and its joint ventures sent 29 crude cargoes to the United States last month versus 42 cargoes in May, a 29 percent fall in the shipped volumes. Compared with exports in June 2016, the decrease was 25 percent.
The main U.S. recipient of Venezuelan crude last month was refining firm Valero Energy. Sales to Citgo Petroleum declined almost 66 percent versus May to 68,400 bpd in June.
OPEC member Venezuela is enduring an economic and political crisis in which opponents of socialist President Nicolas Maduro are calling on him to agree to elections to replace him.
PDVSA's low production and frequent refinery woes have forced the company this year to increase its own crude and products imports amid cash flow problems that have led to delayed payments to suppliers and creditors.
The Venezuelan firm earlier this week awarded companies including Rosneft, Lukoil, Elemento Services and Helsinge several tenders to buy over 15 million barrels of fuels and components for the second half of 2017.
Venezuelan crude sales to the United States recovered temporarily in April to 741,000 bpd, but they started declining again in May. The average for the first half of 2017 was 650,685 bpd, almost 8 percent less than the same period of last year. (Reporting by Marianna Parraga; editing by Grant McCool)