* World stocks tumble towards worst week of the year
* All 30 Dow components in the red in premarket trading
* Apple, Disney among top decliners on the Dow
* Deere falls after reporting drop in profit
* Futures down: Dow 99 pts, S&P 8 pts, Nasdaq 30 pts (Adds details, comment, updates prices)
By Tanya Agrawal
Aug 21 (Reuters) - Wall Street was set to open lower on Friday, with the S&P 500 mini futures falling to their weakest level since early February, as more alarming data from China spooked investors already worried about global growth.
The data from China showed its giant manufacturing sector slowing at the fastest pace since the depths of the financial crisis in 2009, confirming the worries about its health that have preying on economist's minds for months.
That decline comes on the heels of weaker-than-expected data in July, plus this month's turbulent changes in the yuan and a brutal stock market plunge. Shanghai stocks dropped another 4 percent on Friday.
World stock markets tumbled towards their worst week of the year on Friday and commodities had another bruising day.
"There are many, and legitimate, contributing factors to the global economic slowdown narrative. These include China-related issues, such as the recent devaluation of its currency, the stock market's boom and bust in recent months, and slower GDP growth," Nigel Green, CEO of deVere Group, said.
"I believe that this volatility is likely to remain with us, at least until the end of the year ... But for most long term investors, fears of a near-term financial apocalypse are overdone."
Dow e-minis were down 99 points, or 0.59 percent, with 59,555 contracts changing hands. Every one of the 30 Dow components were in the red in premarket trading.
S&P 500 e-minis were down 8.25 points, or 0.41 percent, with 473,756 contracts traded at 8:25 a.m. ET (1225 GMT).
Nasdaq 100 e-minis were down 30.25 points, or 0.69 percent, on volume of 65,857 contracts.
Wall Street had tumbled on Thursday, with the S&P 500 and the Dow closing in the red for the year, on concerns that the decelerating Chinese economy would translate into slower global growth.
Concerns regarding China and a U.S. inflation rate below the expected target has caused some investors to scale back bets that the Federal Reserve will raise interest rates in September.
Dow component Apple's shares resumed their fall and decreased 1.6 percent to $110.84 in premarket trading, a day after a Gartner report on China's slowing smartphone sales.
Disney, another Dow component, fell 1.5 percent to $98.53 after Cowen and Company cut its price target on the stock.
Netflix fell 5 percent to $106.81 as the weakness in media stocks from Thursday looked set to continued.
Deere fell 4.5 percent to $86.60 after the maker of John Deere tractors, reported a 40 percent fall in quarterly profit.
Salesforce.com rose 3.3 percent to $70.07 after it raised its revenue forecast for the full year for the third time. (Reporting by Tanya Agrawal in Bengaluru; Editing by Savio D'Souza)