US STOCKS-Wall Street slumps for third day as earnings disappoint
* Dow in the red for the year
* Caterpillar falls after lower quarterly profit
* GM jumps after adjusted profit more than doubles
* Under Armour jumps to record high after results
* Visa, AT&T and Amazon results expected after the close
* Indexes down: Dow 0.52 pct, S&P 0.45 pct, Nasdaq 0.25 pct (Updates to early afternoon)
By Tanya Agrawal
July 23 (Reuters) - Wall Street fell for the third straight day, with the Dow Jones industrial average lower for the year after disappointing results from bellwethers such as 3M and Caterpillar.
The two stocks, together with American Express, contributed 68 points to the Dow's fall. Continuación...