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By Shashwat Chauhan and Sukriti Gupta

Feb 11 (Reuters) - Wall Street's main indexes dipped on Tuesday as most megacap stocks fell, while investors awaited a testimony from Federal Reserve Chair Jerome Powell for insight on tariffs and their impact on inflation in the world's biggest economy.

Most megacap and growth stocks ticked lower, while some steelmakers extended gains from the previous session, when President Donald Trump substantially raised tariffs on steel and aluminum imports.

Inflation data, due on Wednesday, also dominated market focus ahead of Fed Chair Powell's semiannual monetary policy testimony before the Senate Banking, Housing and Urban Affairs Committee on Tuesday.

Now that there are some actual numbers on tariffs, "(Powell) is going to have to provide some clarity", said Adam Turnquist, chief technical strategist for LPL Financial.

"He can't really punt on those questions because there's enough details where the Fed speaker should have an opinion on at least on some of these measures."

On Wednesday, the January consumer price index $(CPI.UK)$ reading will be released at 8:30 a.m. ET, with Powell set to testify before the House Financial Services Committee later on.

Traders expect at least one 25-basis-point interest-rate cut from the Fed this year, and a 60% chance of another reduction of the same magnitude, according to LSEG data.

Cleveland Fed President Beth Hammack said the need to get inflation back on target will keep monetary policy on pause for now.

Meanwhile, steelmakers Cleveland-Cliffs CLF.N and Steel Dynamics STLD.O rose 2.1% and 1.1%, respectively, a day after Trump announced steel and aluminum levies that are set to take effect on March 4.

Aluminum Century Aluminum CENX.O gained 9.9%.

Trump also said he would follow Monday's action with announcements over the next two days about reciprocal tariffs on all countries that impose duties on U.S. goods.

On Tuesday, megacaps such as Microsoft MSFT.O, Meta META.O, and Tesla TSLA.O were down between 0.4% and 0.9%.

Apple AAPL.O, however, added about 1% after a report said it was partnering with Alibaba 9988.HK to develop and roll out artificial intelligence features for iPhone users in China.

At 09:46 a.m. ET, the Dow Jones Industrial Average .DJI fell 108.74 points, or 0.24%, to 44,361.67, the S&P 500 .SPX lost 14.79 points, or 0.24%, to 6,051.65 and the Nasdaq Composite .IXIC lost 55.41 points, or 0.28%, to 19,658.86.

Seven of the 11 S&P 500 sectors traded lower. Utilities .SPLRCU led losses with a 0.9% fall.

Phillips 66 PSX.N rose 3.8% after activist Elliott Investment Management said it had built a stake of more than $2.5 billion in the oil refiner.

EARNINGS

DuPont de Nemours DD.N gained 4.8% after the industrial materials maker raised its 2025 profit forecast on strong demand for electronics.

Coca-Cola KO.N advanced 3.6% as the beverage maker beat fourth-quarter revenue estimates, helped by higher prices and resilient demand for its sodas and juices.

Fidelity National Information Services FIS.N dropped 16.1% after the banking and payments processing conglomerate forecast first-quarter profit below estimates.

Declining issues outnumbered advancers by a 2.76-to-1 ratio on the NYSE and by a 2.27-to-1 ratio on the Nasdaq.

The S&P 500 posted four new 52-week highs and 13 new lows while the Nasdaq Composite recorded 18 new highs and 113 new lows.

(Reporting by Shashwat Chauhan and Sukriti Gupta in Bengaluru; Editing by Devika Syamnath)

((Shashwat.Chauhan@thomsonreuters.com;))