US stocks have battled through their worst day in 18 months.

The New York stock exchange lost 2 per cent of its value on Thursday as investors reacted to a slowing Chinese economy.

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The S&P 500 and Dow Jones indices both recorded their worst day since February 3, 2014.

Analysts blamed the fall in part on a weakened Chinese economy and an interest rate hike in the US.

“I think the markets are overly pessimistic,” LPL Financial investment strategist Anthony Valeri told CNBC. “I think this sentiment is panicking over news from China, the Fed [and] oil at six-year lows.”

China scared the world last week when it devalued its currency, adding to worries of a broader economic slowdown.

“I think the oil and the geopolitical problems are the real problems for the market because we’re looking at lower global economic growth, and lower global growth is going to weigh on the U.S. as well,” Rockwell Global Capital chief market economist Peter Cardillo told CNBC.