US STOCKS-Wall St falls as Greece crisis deepens; Fed meet eyed
* Greece talks suffer setback after IMF quits
* Consumer confidence surges in June
* Next week's Fed policy meeting eyed
* Wingstop soars in IPO debut
* Twitter rises after CEO quits abruptly
* Indexes down: Dow 0.8 pct, S&P 0.7 pct, Nasdaq 0.5 pct (Updates to early afternoon)
By Tanya Agrawal
June 12 (Reuters) - U.S. stocks erased most of their gains for the week as investors stayed on the sidelines ahead of a Federal Reserve policy meeting next week and as Greek debt talks hit a stalemate.
The S&P 500 was set to end unchanged for the week, while the Nasdaq Composite was on track to close down for the third straight week. Continuación...