US STOCKS-Futures drop on euro zone debt concerns

* Portugal set to vote on austerity measures

* U.S. February new home sales data on tap

* Futures off: S&P 1 pts, Dow 4 pts, Nasdaq off 9.25 pts

* For up-to-the-minute market news see [STXNEWS/US] (Adds byline, quote, Egypt Index ETF in premarket trade)

By Angela Moon

NEW YORK, March 23 (Reuters) - U.S. stock index futures fell on Wednesday, after modest losses in the previous session, as worry continued over debt issues in the euro zone, Japan's nuclear crisis and violence in the Middle East and North Africa.

Concerns over euro area debt levels will again be in focus as Portugal's parliament was expected to reject government austerity measures in a vote scheduled for 1500 GMT, with Prime Minister Jose Socrates threatening to resign if the opposition rejected the proposals. For details, see [ID:nLDE72L1IO]

"The opposition wants to vote no, and if the budget deal fails, the Socrates government will fall, and hat in hand the country will go to the EU/IMF," said Peter Boockvar, equity strategist at Miller Tabak & Co in New York.

The Egyptian stock exchange's broad index <.EGX100> tumbled on Wednesday after the bourse reopened following a seven-week closure caused by political turmoil. In the U.S., Market Vectors Egypt Index ETF fell 4.5 percent in premarket trade.

U.S.-listed Japanese stocks will be in focus as further disruptions to supply chains were seen hitting individual companies in the wake of Japan's massive earthquake, with Sony Corp cutting output at five more plants and Toyota Motor saying it would keep assembly lines shut until at least Saturday. [ID:nL3E7EN0ND]

Ford Motor Co , however, said it had saw no immediate impact or disruption from the earthquake. [ID:nSGE72A049]

Japan estimated direct damage from the earthquake and tsunami to be 16-25 trillion yen ($185-$308 billion), making it the world's costliest natural disaster. [ID:nL3E7EM3MC]

U.S. new home sales data for February is due at 10 a.m. Economists in a Reuters survey expect new sales have likely risen to a 290,000 annual rate from January's 284,000.

S&P 500 futures were down 1 points, and below fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures fell 4 points, and Nasdaq 100 futures dropped 9.25 points.

General Motors Co sold its preferred shares in auto lender Ally Financial Inc for $1 billion to strengthen its balance sheet. [ID:nN22193913]

Wall Street snapped a three-day winning streak on Tuesday, with trading volume the lowest of the year. (Editing by Padraic Cassidy)