Oil prices plunged more than $1 during trading on Thursday on hopes of a potential U.S.-Iran nuclear deal, while a surprise build in U.S. crude inventories last week raised investor concerns about a supply glut.

Brent crude fell $1.49, or 2.3%, to $64.60 a barrel by 0405 GMT. U.S. West Texas Intermediate (WTI) crude fell $1.46, or 2.3%, to $61.69.

Both benchmarks fell about 0.8% on Wednesday.

Iran is willing to agree to a deal with the U.S. in exchange for the lifting of economic sanctions, an Iranian official told NBC News in an interview published Wednesday. "The renewed selling was fueled by expectations that the U.S.-Iran nuclear deal will ease recently tightened U.S. sanctions on Iran, potentially loosening the global crude supply-demand balance," said Yuki Takashima, an economist at Nomura Securities.

Saudi Arabia fully supports U.S.-Iran nuclear talks and hopes for a positive outcome, the kingdom's foreign minister Prince Faisal bin Farhan Al-Saud said on Wednesday.

Washington imposed sanctions on Wednesday to target Iran's efforts to produce ballistic missile components domestically, the U.S. Treasury Department said, following Tuesday's sanctions on about 20 companies in a network it said had long shipped Iranian oil to China.

The sanctions came after the fourth round of U.S.-Iran talks in Oman aimed at resolving disputes over Iran's nuclear program. A surprise rise in U.S. inventories overnight also weighed on prices as did profit-taking after crude rebounded to the recent highs of the $55-65 a barrel range, said Tony Sycamore, an analyst at IG.

"My expectation is that we're going to continue to see the market in a range for the next month or so, but unless there's some unexpected geopolitical shock, when that range really changes, it's going to be down towards $50 a barrel," he said.

Data from the Energy Information Administration showed crude inventories rose by 3.5 million barrels to 441.8 million barrels in the week to May 9, compared with analysts' expectations in a Reuters poll for a draw of 1.1 million barrels.

API industry data also showed a big build of 4.3 million barrels in crude inventories last week, market sources said on Tuesday. The Organization of the Petroleum Exporting Countries and allied producers, known as OPEC+, have been increasing supply, although OPEC on Wednesday cut its forecast for oil supply growth from the United States and other producers outside the broader OPEC+ group this year. (Newsmaker23)

Source: Reuters