NEW YORK Stock index futures pointed to a weak start for Wall Street on Wednesday, with futures for the S&P 500, Dow Jones futures and Nasdaq futures down 0.2 to 0.4 percent by 5:06 a.m. EDT.
* Caution over the euro zone debt crisis resurfaced after Moody's became the first ratings agency to cut the credit rating for Portugal by four notches to non-investment grade, known as junk, warning the country may need a second round of rescue funds before it can return to capital markets.
* The euro lost ground against the dollar and the Swiss franc on euro zone debt worries and peripheral euro zone banking stocks fell across the board.
* U.S. stocks ended mainly flat in thin trade on Tuesday, as investors paused after last week's rally.
* The ISM non-manufacturing index, due at 1400 GMT, is expected to show a slight dip to 54.0 in June from 54.6, according to a Reuters poll, the second-lowest reading since last August.
* Other data scheduled for release include the Challenger planned layoffs for June at 1130 GMT and weekly mortgage index numbers at 1100 GMT.
* In company news, Berkshire Hathaway Inc
* U.S. pipeline safety regulators on Tuesday said Exxon Mobil
* Global passenger airplane market over the next 20 years is seen at $4 trillion, Boeing Co
* In Europe, the FTSEurofirst 300 index <.FTEU3> of top shares was lower in early trade, ending a seven-day winning steak on concerns about the euro zone debt crisis and the possibility of contagion after Moody's cut Portugal's credit rating.
(Reporting by Harpreet Bhal, editing by Jane Merriman)