New Delhi, April 21 -- Crude oil prices declined more than 1% at Monday's open in Asia as nuclear talks between the United States and Iran progressed, easing supply concerns.

Brent crude futures slipped 1.50%, to $66.94 a barrel, while US West Texas Intermediate crude fell 1.52% to $63.70 a barrel.

Crude oil prices have declined sharply this month, touching a four-year low at one point. Trading volumes in crude futures may be lower than usual in Monday's session, with some countries observing holidays to mark Easter.

US and Iran agreed on Saturday to begin drawing up a framework for a potential nuclear deal, Iran's foreign minister said, after talks that a US official described as yielding "very good progress", Reuters reported.

The d...