* Wal-Mart falls after cutting full-year forecast
* Chinese stock slumps, yuan devaluations fears resurface
* Oil prices, copper near six-year lows
* July housing starts beat expectations; at nearly 8-year high
* Home Depot, TJX rise after results
* Futures down: Dow 56 pts, S&P 5 pts, Nasdaq 13 pts (Adds details, comment, updates prices)
By Tanya Agrawal
Aug 18 (Reuters) - Wall Street was set to open lower on Tuesday, weighed down by a 6 percent slump in Chinese shares and disappointing results from Wal-Mart.
Wal-Mart shares fell 2.6 percent to $70.05 in premarket trading after the Dow component reported weaker-than-expected quarterly earnings and lowered its full-year forecast. The stock was the biggest loser on the Dow Jones industrial average.
Chinese stocks plunged again as the yuan weakened against the dollar, reigniting fears that Beijing may be intent on a deeper devaluation of the currency despite the central bank's comment that it sees no reason for a further slide.
The People's Bank of China devalued the currency last week by nearly 2 percent, triggering an avalanche of selling by investors across the world who feared Beijing wanted to engineer a much sharper decline to support weak exports.
U.S. oil prices and industrial metals, including copper, also traded near six-year lows, adding to the bearish market sentiment amid worries over China's growth outlook.
"The problem in China is that the markets haven't been released for free and open trading and until that happens there is going to continue to be downside pressure," said Randy Frederick, managing director of trading and derivatives for Charles Schwab in Austin, Texas.
S&P 500 e-minis were down 5.25 points, or 0.25 percent, with 154,413 contracts traded at 8:35 a.m. ET (1235 GMT).
Nasdaq 100 e-minis were down 13.25 points, or 0.29 percent, on volume of 20,349 contracts.
Dow e-minis were down 56 points, or 0.32 percent, with 21,379 contracts changing hands.
Home Depot was the only Dow component in the green premarket, up 1.1 percent at $121.05, after the home improvement retailer reported a better-than-expected rise in quarterly same-store sales.
Home improvement companies and home builders are enjoying a spot in the sun from storing results and economic data.
Data on Tuesday showed U.S. housing starts rose to a near eight-year high in July as builders ramped up construction of single-family homes. This follow a Monday report showing U.S. homebuilder sentiment in August rose to a near decade-high.
Economic data points are being carefully evaluated by investors to gauge when the U.S. Federal Reserve will raise interest rates.
Although the health of the U.S. economy appears to be stabilizing, the effect of the yuan devaluation and other macro factors are playing on investor's minds.
Investors are still not fully convinced the Fed will raise rates in September, but most are betting a rate hike will occur by the end of year. With the earning season winding down, all eyes are on the Wednesday minutes of the Fed's latest meeting.
In retail earnings, TJX Cos, rose 3.7 percent to $74.27 after it reported a rise in quarterly sales.
National Penn Bancshares rose 14.6 percent to $12.51 after BB&T said it would buy the bank for about $1.8 billion. BB&T fell 2.7 percent to $39.10. (Reporting by Tanya Agrawal in Bengaluru; Editing by Savio D'Souza)