U.S. stock futures edged lower early Tuesday, signaling a cautious start for Wall Street as investors looked ahead to a heavy week of market-moving events. Futures linked to the S&P 500 were down slightly in early trading, with attention centered on upcoming results from major companies and the next Federal Reserve rate decision.

The weakness in U.S. futures came alongside sharp losses in Asia. South Korea's Kospi plunged 10%, highlighting the broader risk-off tone across global markets and underscoring how nervous investors remain ahead of key economic and corporate updates.

This week is especially important for traders because it combines two major catalysts: earnings from mega-cap companies and the Fed's latest policy meeting. Together, those events could shape expectations for interest rates, corporate growth and overall market direction in the near term.

For now, the early moves suggest investors are taking a more defensive stance. With stock futures slipping and the Kospi posting a steep decline, markets appeared focused on managing uncertainty before more clarity arrives from company reports and the central bank.