Crude oil rallies after biggest daily retreat in 10 sessions.

Investors are watching a June 30 deadline for Iran and six other nations to reach a nuclear deal that could lift oil sanctions. European policy makers expressed confidence that a deal with Greece was within reach after Prime Minister Alexis Tsipras's government submitted a last-minute set of proposals they said could end a five-month standoff over aid. The U.S. and five other world powers are offering Iran relief from sanctions, including oil exports, if the Islamic Republic curtails its nuclear program and allows inspections to verify compliance. [Extracted from the article]