The corporate logo of the state oil company PDVSA is seen at a gas station in Caracas, Venezuela, August 30, 2017. REUTERS/Andres Martinez Casares

HOUSTON (Reuters) - Venezuelan crude sales to the United States in August were largely unchanged at 638,935 barrels per day (bpd) compared with the prior month, but continued to fall far short of year-earlier levels, according to Thomson Reuters Trade Flows data.

State-run oil company PDVSA has sought to increase exports of diluted crude oil (DCO), a blend of imported naphtha and extra heavy oil from the Orinoco Belt, Venezuela’s largest producing region.

But declining output of other grades and problems obtaining short-term financing due to a growing risk of default and sanctions imposed by the United States have affected PDVSA’s shipments to the United States in recent months.

The closure of several Texas oil ports and refineries at the end of August ahead of Hurricane Harvey also affected the imported volumes.

PDVSA and its joint ventures sent a total of 38 crude cargoes to the United States in August versus 36 in July. The August volume was 0.1 percent higher than the previous month, but 10 percent lower than in the same month of 2016.

Refining firm Valero Energy was the largest receiver of Venezuelan crude in the United States last month, followed by PDVSA’s U.S. unit Citgo Petroleum.

U.S. refiner Phillips 66, which in July did not receive supplies of Venezuelan oil, in August imported 121,000 bpd of Merey heavy crude, according to the data. Chevron Corp bought 103,000 bpd for its Pascagoula refinery in Mississippi.

President Donald Trump’s administration in August imposed sanctions intended to disrupt PDVSA and the Venezuelan government’s ability to raise new debt, and banned Citgo from transferring dividends or other profits to its parent company.

The measures followed a list of 31 Venezuelan officials sanctioned this year, including President Nicolas Maduro and PDVSA’s finance boss, Simon Zerpa, in an effort to halt financing that the White House said fuels a “dictatorship” in the South American country.