Walmart Inc's WMT.N shares slumped 9.1% in premarket trading, while Target TGT.N and Amazon.com AMZN.O fell 5%, souring the mood as some of America's biggest companies report in what is set to be the busiest week of the earnings season. Investors are also bracing for a widely expected 75 basis-point rate hike by the Federal Reserve at the end of its two-day policy meeting, which gets under way later on Tuesday. Along with high inflation, a stronger dollar is also expected to pressure earnings of companies with sprawling global operations.