Energy stocks were lower Monday afternoon, with the NYSE Energy Sector Index dropping 3.1% and the State Street Energy Select Sector SPDR ETF (XLE) falling 2.7%.

The Philadelphia Oil Service Sector Index was down 2.4%, and the Dow Jones US Utilities Index rose 1%.

The US and Iran have reached an agreement to end their war and reopen the crucial Strait of Hormuz after more than three months of conflict that disrupted regional stability and global shipping routes. "The deal with the Islamic Republic of Iran is now complete," President Donald Trump said in a social media post on Sunday. "I hereby fully authorize the toll free opening of the Strait of Hormuz, and, simultaneously herewith, authorize the immediate removal of the US Naval blockade."

Front-month West Texas Intermediate crude oil fell 5.1% to $80.59 a barrel, and the global benchmark Brent crude contract dropped 4.7% to $83.26 a barrel. Henry Hub natural gas futures rose 0.3% to $3.13 per 1 million BTU.

In corporate news, Peabody Energy (BTU) said Monday it terminated its amended 2020 transaction support agreement with surety providers and entered into standard indemnification agreements to support its US mine reclamation obligations. Peabody Energy shares were down 4.7%.