US stocks drop as investors weigh shutdown risks and tighter Fed

• Stock futures dropped Tuesday, extending September's market sell-off.
• Federal Reserve hawkishness and the possibility of a US shutdown are adding downside pressure.
• JPMorgan's Jamie Dimon forecast that interest rates could reach as high as 7%.

Stocks fell Tuesday morning, extending this month's market downturn and canceling out most of Monday's gains.  

Among headwinds traders are assessing is the expectation of tighter monetary policy, after the Federal Reserve indicated chances of another rate hike this year.