Wall Street cuts gains on 'fiscal cliff' worry

Dow Jones adds 0.3%, S&P 500 gains 0.5% and Nasdaq up 0.6%

US stocks cut early gains in a volatile start to the session on Thursday as investors looked to lawmakers in Washington to resolve the budget impasse that has been unsettling markets.

The Dow Jones Industrial Average gained 42.04 points, or 0.32%, to 13,027.15. The Standard & Poor's 500 Index gained 5.63 points, or 0.40%, to 1,415.56. The Nasdaq Composite Index gained 16.64 points, or 0.56%, to 3,008.42.