CARACAS (Reuters) - A grace period on Chinese loans to Venezuela has lapsed, according to two Venezuelan sources with knowledge of the matter, potentially depriving the cash-strapped OPEC nation of billions of dollars in desperately needed oil revenue this year.

A sculpture is seen outside a building of Venezuela's state oil company PDVSA in Caracas, Venezuela June 14, 2016. REUTERS/Ivan Alvarado

China eased the payment terms two years ago on some $19 billion in oil-for-loan deals, under which Venezuela sends shipments of crude oil and fuel to pay off debt, allowing Venezuela to make interest-only payments.

The favorable conditions from Beijing helped President Nicolas Maduro’s socialist government weather a collapse in Venezuela’s economy, which slid into hyperinflation and a painful recession following a downturn in oil prices.

But the grace period has lapsed without a renewal in recent weeks, according to the sources, who have been briefed by Chinese and Venezuelan officials.

That could deprive Venezuela of some $7 billion in annual revenue, according to a Reuters’ estimate based on current oil prices, a crippling blow to a country already struggling to import basic goods like food and medicine.

The sources, who asked not to be identified, said that Venezuela continues to press for an extension but is responsible for making the full payments while the talks continue.

The sharply increased payments would absorb roughly an additional 305,000 barrels per day (bpd) of Venezuela’s oil production, which has fallen to a 33-year low this year.

State oil company Petroleos de Venezuela SA’s (PDVSA) deteriorating infrastructure and cash flow have caused oil production to plunge 33 percent in a year, to 1.51 million bpd in March, according to official data reported to OPEC.

“China maintains its position of not increasing its exposure to Venezuela and is adjusting conditions, given that the price of oil is now $20 per barrel above its level when the (grace period) was created,” said one of the sources.

Neither Venezuela’s Information Ministry nor state oil company PDVSA responded to requests for comment.

China Development Bank, which has underwritten most of the loans to Venezuela, did not respond to a request for comment.

China’s Foreign Ministry, asked about the negotiations, said that cooperation was proceeding smoothly and the loan contracts were in accord with international standards.

Caracas could seek to preserve cash flow by sending those barrels to other clients who pay cash, defaulting on its obligations to China in the process and straining ties with a crucial political ally and its largest financier.

Beijing would have little incentive to pursue an embarrassing commercial dispute with a government it supported for years, and may simply turn a blind eye to a default.

Maduro, who is up for re-election on May 20, says his country is victim of an “economic war” led by his political adversaries with the help of Washington.

His critics say the country’s plight is the result of a dysfunctional state-led economic model.

CHINA MORE PRAGMATIC

China for a decade courted the government of then-President Hugo Chavez with generous financing arrangements as it sought to secure oil supplies for its resource-hungry economy and cultivate an anti-Washington ally in Latin America.

It extended more than $50 billion in credit to Venezuela over 10 years.

However, Beijing stopped renewing loans three years ago as Venezuela’s economy began spiraling downward as a result of the crash of oil prices.

Last year, Venezuela shipped some 700,000 bpd of crude and fuel to China through bilateral agreements, according to a Reuters review of PDVSA trade documents.

But only around 70,000 bpd were applied to debt service under the grace period arrangement, according to one of the sources, with China paying the remainder in cash.

Without the grace period, the amount applied to debt service rises to 375,000 bpd, the sources said.

Venezuela and PDVSA are in default on nearly $50 billion in international bonds because they have failed to make more than $2 billion in interest payments.

Bondholders have yet to take legal action, in part because most believe Maduro is unwilling to make changes to revive the economy, and because U.S. sanctions effectively block them from buying any newly issued Venezuelan bonds, making a restructuring practically impossible.

PDVSA also has hundreds of millions of dollars in outstanding bills to suppliers and partners.

Italian energy company Eni ENI.MI said on Friday that PDVSA's debt had risen to 650 million euros ($787 million) from 600 million euros in February and that payments were "near zero."

($1 = 0.8262 euros)