Venezuela's president ordered a review of ties with Washington after uncovering allegations the United States was spying on employees at the state oil company.

President Nicolas Maduro said his administration received documents suggesting the U.S. National Security Agency spied on workers with Petroleos de Venezuela, known also as PDVSA, by intercepting phone calls and emails from former Energy Minister Rafael Ramirez.

Maduro was quoted by Univision as saying his administration "will initiate a comprehensive review of the relationship with the U.S. government because Venezuela is respected."

The president referenced reports from The Intercept, teleSUR and the Wall Street Journal saying U.S. officials were looking into allegations of corruption at PDVSA. Many of the allegations were revealed by NSA leaker Edward Snowden.

Venezuela is the No. 4 crude oil exporter to the United States, after Canada, Saudi Arabia and Mexico, respectively. Crude oil exports of 703,000 barrels per day for the week ending Nov. 13 were 25 percent lower than for the same week in 2014.

In March, the U.S. government sanctioned seven Venezuelan officials for human rights offenses, saying Washington was "deeply concerned" by the culture of political intimidation in Caracas.

Diosdado Cabello, speaker of the Venezuelan Congress, said the sanctions were an open threat from Washington. Maduro in October threatened to sue the United States after it said Venezuela was a threat to U.S. national security.

The Central Bank of Venezuela blamed last year's collapse in oil prices for a drop in gross domestic product. High inflation in the country is eroding consumer purchasing power, which in turn has led to frustration with the Maduro administration.

Maduro has faced mounting pressure from his opponents at least since taking the reins in Caracas after his predecessor Hugo Chavez died in 2013. María Corina Machado, a former assemblywoman who helped lead protests against Maduro last year, recently called on Pope Francis to step in to a fracturing Venezuela.