Oil prices settled lower on Tuesday as traders awaited outcome of the Iranian nuclear talks, which could pave the way for more Iranian crude oil adding to a persistent global oil glut. Prices logged losses for the month as well as the quarter on the back of excess supply and tightening storage in the U.S. On the New York Mercantile Exchange, crude for delivery in May settled at $47.60 a barrel, down $1.08, or 2.2% from Monday’s settlement. Based on the front-month contracts, prices lost 4.3% for the month and were down 10.6% for the quarter. May-dated Brent crude fell $1.18, or 2.1%, to $55.11 a barrel on London’s ICE Futures exchange, with prices down 11.9% for the month and losing 3.9% for the quarter.

Talks over Iran’s nuclear program could continue into Wednesday, extending a key deadline that had been set for this evening, White House spokesman Josh Earnest said Tuesday. Many in the oil market fear that if the sanctions are lifted, Iran, which holds around 10% of the world’s oil reserves and almost a fifth of global gas reserves, would ramp up production and exports. “At this point, it seems they are agreeing to defer attacking the key issues; they are unable to compromise and are kicking the can until June 30,” said Matt Smith, a commodity analyst at Schneider Electric. June 30 is the deadline for a final agreement. Iran may have a sizable inventory in floating storage, ready to be released upon the lifting of oil sanctions, he said. But “the reality is that it would still be a gradual and protracted return of its production to the global market in the next year or so.”

Meanwhile, investors are bracing for the weekly U.S. oil-inventory data from the American Petroleum Institute late Tuesday and on Wednesday from the U.S. Energy Information Administration. Analysts polled by Platts forecast an increase of 3.5 million barrels in crude stockpiles for the week ended March 27.