Wall Street's main indexes were set to bounce back on Wednesday following a sharp sell-off triggered by concerns over rising inflation and the new Omicron coronavirus variant, while shares of Merck rose on progress in the approval of its COVID-19 pill.

Merck & Co Inc gained 1.1% in premarket trading after a panel of advisers to the U.S. Food and Drug Administration narrowly voted to recommend the agency authorize the drugmaker's antiviral pill to treat COVID-19.

U.S. stocks slumped on Tuesday after Federal Reserve Chair Jerome Powell in his testimony before the Senate Banking Committee indicated that he no longer considers inflation as "transitory."

Powell also said the U.S. central bank would consider bringing forward plans for tapering its bond buying program at its next meeting in two weeks.

"Most investors realized that the Fed was going to have to shift course somewhat ... there's plenty of people that feel inflation is a bigger problem, and maybe a bigger risk to the market would be the Fed failing to take any action that recognizes that," said Rick Meckler, partner, Cherry Lane Investments in New Vernon, New Jersey.

"Coming to the year-end, where markets can be a little less liquid, we are likely to see some back and forth until we get more information (on Omicron)."

Investors were also awaiting a Fed report, known as the "Beige Book," on current economic conditions to provide further insight into the central bank's stance on inflation. The report is due at 2:00 p.m. ET (1900 GMT).

Powell's seemingly hawkish comments on Tuesday served as a double whammy for markets, which were already nervous about the spread of the Omicron variant and its potential to hinder a global economic recovery.

The Fed chair is also due to testify before a House Financial Services Committee hearing at 10 a.m. ET.

A World Health Organization official said some of the early indications were that most Omicron cases were mild, with none severe.

Travel and leisure stocks rebounded, with cruiseliners Norwegian Cruise Line, Carnival Corp and Royal Caribbean rising between 2.2% and 3.2%.

Occidental Petroleum, which led gains among energy stocks, was up 3.4% as oil prices climbed 3%. Shares of major Wall Street lenders also moved higher after steep falls on Tuesday.

At 8:20 a.m. ET, Dow e-minis were up 300 points, or 0.87%.

The S&P 500 e-minis were up 55.5 points, or 1.22%, and Nasdaq 100 e-minis were up 212.5 points, or 1.32%, supported by shares of Amazon.com, Apple Inc, Tesla Inc, Google owner Alphabet Inc, Meta Platforms and Microsoft Corp. All these tech companies added between 1.2% and 1.7%.

Meanwhile, data showed U.S. private employers maintained a strong pace of hiring in November. Readings on manufacturing activity are due after market open.

Salesforce.com Inc forecast current-quarter profit below estimates as it faces stiff competition from rivals including Microsoft, sending its shares down 6.2%.