U.S. stocks opened lower Tuesday, pressured by news that crude futures once more are nearing the key $60 a barrel level. In recent trades, the Dow Jones Industrial Average was down 20 points at 10,283, the Nasdaq Composite down 3.15 points at 2,054, and the S&P 500 down 1 point at 1,193. Moving against the negative trend, Wal-Mart Stores was up $1.21 at $49.49, after lifting its June sales forecast over the recent July Fourth holiday weekend.