US STOCKS-S&P 500 posts worst day since April; indexes down for month
* Fears over earlier Fed rate hike spur selling
* Investors fret over Argentina default fallout, Russia tensions
* Exxon falls after results
* Labor costs post largest gain in more than 5-1/2 years
* Dow down 1.9 pct, S&P 2 pct, Nasdaq 2.1 pct (Updates to close)
By Caroline Valetkevitch
NEW YORK, July 31 (Reuters) - The S&P 500 posted its worst daily decline since April and first monthly drop since January on Thursday as economic data sparked concern that the Federal Reserve could raise interest rates sooner than some have expected.
Data showing that U.S. labor costs recorded their biggest gain in more than 5-1/2 years in the second quarter came a day after the Fed upgraded its assessment of the U.S. economy while reiterating it was in no hurry to raise rates.
Problems in overseas economies added to the bearish tone, with Argentina defaulting on its debt for the second time in 12 years. Continuación...