Mumbai, June 17 -- Oil prices sank again Tuesday and dropped below $80 per barrel for the first time since early March while U.S. stocks drifted near their all-time highs in mixed trading.

The S&P 500 slipped 0.6% and pulled 1.3% below its record set earlier this month. The market was nearly evenly split between stocks rising and falling, and the Dow Jones Industrial Average added 328 points, or 0.6%, to set a record for the second straight day. But drops for some influential tech stocks pulled the Nasdaq composite down 1.2%.

The strongest action was in the oil market, where optimism continued that a tentative U.S.-Iran deal on their war will reopen the Strait of Hormuz at the end of the week and get the global flow of oil going again. ...