US STOCKS-Wall St falls on Greek default fears, volatility spikes
* Greece will not pay IMF on Tuesday: Govt official
* Nine of 10 S&P sectors in the red
* Financials weigh heavily on the S&P
* CBOE Volatility index spikes 29 pct
* Euro STOXX 50 index - biggest one-day fall since 2011
* Indexes down: Dow 1.46 pct, S&P 1.55 pct, Nasdaq 1.82 pct (Updates prices, adds market commentary, changes byline)
By Sinead Carew
June 29 (Reuters) - U.S. stocks extended their losses in heavy trading on Monday after a collapse in Greek bailout talks intensified fears that the country could be the first to exit the euro zone.
Greece appeared to confirm it was heading for a default after a government official said the country would not pay a 1.6 billon euro loan installment due to the International Monetary Fund on Tuesday. Continuación...