US stocks opened slightly lower Monday ahead of a keenly anticipated Federal Reserve meeting later this week that could result in the first interest rate hike in over nine years.

Five minutes into trade, the Dow Jones Industrial Average was at 16,411.31, down 21.78 points (0.13 percent).

The broad-based S&P 500 dipped 2.36 (0.12 percent) to 1,958.69, while the tech-rich Nasdaq Composite Index was essentially flat, dropping 0.21 to 4,822.13.

Commentators are divided in their predictions for the Fed, which has signaled it plans to lift benchmark interest rates some time in 2015.

However, that target has been complicated by stubbornly low inflation and turbulence in global financial markets sparked by a big retreat in Chinese equities. The central bank's two-day policy meeting ends Thursday.