U.S. index futures swung between gains and losses Wednesday as investors turned cautious ahead of Federal Reserve Chairman Jerome Powell's congressional testimony, while Tesla gained as Texas requires charging stations to include its plug.

Powell is due to deliver his semiannual monetary policy testimony before the House Financial Services Committee at 10 a.m. ET (1400 GMT), and is expected to be questioned on whether rates will rise again in July.

Money markets see a 77% chance of the Fed raising the benchmark rate in July by 25 basis points, the last one in rate hike cycle, according to CMEGroup's Fedwatch tool.

"Since the last Fed meeting, some of the narrative was confusing to most investors," said Peter Andersen, founder of Andersen Capital Management.

"A lot of questions will be focused on the path forward, and they will be looking for some indication that they (Fed) may signal that the rate hikes are more likely to be paused permanently."

Yields on the 2-year treasury notes, which move in line with interest rate expectations, and 10-year notes rose marginally on Wednesday.

In the previous session, Wall Street's main indexes fell as investors booked profits in the wake of a sustained market rally amid signs of weakening global demand. Still, the benchmark S&P 500 has advanced 14.3% so far this year.

If a U.S. recession becomes more likely, Goldman Sachs said investors should maintain upside exposure to equities by using options to hedge a potential 23% fall in the S&P 500 index.

It holds chances of a recession at 25%, and in that base case, it expects the S&P 500 to rise to 4,500 - about 2.5% higher than current levels.

Among individual movers, Tesla Inc added 1.4% premarket as Texas requires EV charging companies to include both Tesla's standard as well as the nationally recognized CCS if they want to be part of a state program to electrify highways using federal dollars.

At 7:03 a.m. ET, Dow e-minis were down 17 points, or 0.05%, S&P 500 e-minis were down 1.25 points, or 0.03%, and Nasdaq 100 e-minis were down 12.5 points, or 0.08%.

FedEx shares slid 2.8% in premarket trading after the shipping firm missed quarterly earnings expectations and said global shipping downturn has hurt margins for the sector.

Crypto firms including Coinbase, Riot Platforms, Marathon Digital and Bit Digital rose between 2.5% and 6.7%, tracking an uptick in Bitcon prices, which hit highest level in six weeks.

U.S.-listed shares of Chinese electric vehicle (EV) makers Li Auto, Nio Inc and Xpeng Inc added between 1.8% and 3.5% as China unveiled 520 billion yuan ($72.3 billion) worth of tax breaks to boost sales of EVs and other green cars over the next four years.

Investors will also parse remarks by other Fed policymakers including Chicago Fed's Austan Goolsbee, a voting member this year, and Cleveland Fed's Loretta Mester later in the day for more clues on the monetary tightening path.