Pfizer rose 2.6 percent as it lifted some of its full-year projections, while Uber surged more than 15 percent as quarterly revenues jumped 72 percent to $8.3 billion.

Analysts also cited hopes about a China policy shift on Covid-19 restrictions after a post on social media suggested Chinese officials were forming a committee to discuss rolling back some of the country's economically painful zero-Covid policies.

Adam Sarhan of 50 Park Investment said the market sentiment has improved as suggested by the reaction to the recent batch of mixed earnings.

"We're seeing a subtle but very important shift with investors' risk appetite, or their appetite with respect to risk," Sarhan said, noting a consensus that the Federal Reserve will soon "pivot" from a monetary policy of severe interest rate hikes to counter inflation.

About 20 minutes into trading, the Dow Jones Industrial Average was up 0.4 percent t 32,855.24.

The broad-based S&P 500 added 0.6 percent at 3,894.71, while the tech-rich Nasdaq Composite Index rose 0.8 percent to 11,073.06.

The Fed is scheduled to kick off a two-day policy meeting expected to conclude Wednesday with another large interest rate increase.

Fed Chair Jerome Powell will update markets on the central bank's current thinking, including the possibility the Fed could soon moderate its stance.