Apple, a Dow component and important contributor to the Nasdaq, shot up around five percent after reporting better-than-expected quarterly earnings after the close Tuesday.

Investors are betting the Fed will announce a long-anticipated interest rate cut at 1800 GMT, and they will be watching closely for signals that more stimulus is on the way.

About 15 minutes into trading, the Dow Jones Industrial Average was up 0.3 percent at 27,280.37.

The broad-based S&P 500 edged up 0.1 percent to 3,015.92, while the tech-rich Nasdaq Composite Index gained 0.2 percent to 8,291.46.

Analysts say the cut in the benchmark lending rate has been largely priced in, although any Fed hints on the possibility of additional actions could move the market.

The Fed meeting comes as data from payrolls data firm ADP estimated the US added 156,000 private-sector jobs in July, slightly more than expected. The official government employment data will be released Friday.

In another issue closely watched by markets, US and Chinese negotiators concluded trade talks in Shanghai, reaching no deal but agreeing to convene again in September in Washington.

"The two sides conducted frank, highly efficient and constructive in-depth exchanges on major issues of common interest in the economic and trade field," according to the official Xinhua news agency.

The White House said Beijing "confirmed their commitment" to buy US farm goods -- something President Donald Trump complained about Tuesday on Twitter.

However, trade experts say it now appears unlikely a deal will be finalized before presidential elections next year.

Among other companies reporting results, Electronic Arts surged 8.7 percent, Advanced Micro Devices slumped 7.8 percent and General Electric rose 0.2 percent.