Crude-oil prices fell Thursday after six world powers and Iran announced they had agreed on a framework to curb Iran's nuclear drive.
The US benchmark,  West Texas Intermediate (WTI) for May delivery, shed 95 cents to close at $49.14 a barrel on the New York Mercantile Exchange.
Brent North Sea crude for delivery in May, the global benchmark futures contract, slumped to $54.98 in late London trade, a sharp decline of $2.12 from Wednesday's closing level.
The market has been following the marathon negotiations closely, estimating that an agreement could lift sanctions against Iran, allowing the return of Iranian crude to an oversupplied global market.
Shortly before the New York market closed, the world powers and Iran said that Tehran has agreed to curtail its nuclear program in return for the lifting of sanctions that have harmed its economy.
At the beginning of the press conference in Lausanne, Switzerland, the price of WTI, which had been trading lower since the market opened, fell to $48.11 a barrel before paring its losses.
The countries announced the drafting of a full agreement would begin immediately, with a June 30 deadline for completion.
Sanctions would be lifted upon Iran's fulfillment of the terms of the deal, aimed at preventing Tehran from developing nuclear weapons.
"If Iran cheats, the world will know it," US President Barack Obama said, adding that the deal reached was based not on trust but on "unprecedented verification."