* Financials biggest laggards on S&P
* Benchmark U.S. 10-year yields hit 3-week low
* Indexes down: Dow 0.97 pct, S&P 1.05 pct, Nasdaq 1.49 pct (Adds quote and detail on market moves, updates prices)
By Noel Randewich
March 21 (Reuters) - Wall Street fell sharply on Tuesday as investors worried that President Donald Trump will struggle to deliver promised tax cuts that propelled the market to record highs in recent months, with nervousness increasing ahead of a key healthcare vote.
The S&P 500 and Dow Jones Industrial Average lost around 1 percent and were on track for their worst one-day percentage declines since before Trump's election victory in November.
The S&P financial index dropped 2.47 percent and was heading for its biggest daily fall since June. That added to losses in the sector since the Federal Reserve last week raised interest rates by 25 basis points and signaled it would remain on a gradual pace of hikes, a less aggressive stance than some investors expected.
Banks benefit from higher interest rates and their stocks are sensitive to changes in expectations of how quickly the Fed will change rates.
Bank of America slumped 5.48 percent, the biggest drag on the S&P 500, while a 2.98 percent drop in Goldman Sachs pulled the Dow lower.
"There was a feeling the Fed was going to possibly be more hawkish last week. That didn't happen," said Mark Kepner, managing director at Themis Trading in Chatham, New Jersey. "That takes a little out of the higher rates that the banks want."
Benchmark 10-year U.S. Treasuries US10YT=RR were last up 10/32 in price to yield 2.44 percent, the lowest yield since March 1.
Republican party leaders aim to move controversial healthcare legislation to the House floor for debate as early as Thursday. But they can only afford to lose about 20 votes from Republican ranks, or risk the bill failing, since minority Democrats are united against it.
With valuations stretched, investors see the Trump administration's struggles to push through the healthcare overhaul as a sign he may also face setbacks delivering promised corporate tax cuts. Expectations of those tax cuts are a major reason for the 10-percent surge in the S&P 500 since Trump's election in November.
"The market is starting to get a little fed up with the lack of progress in healthcare because everything else is being put on the back burner," said RJ Grant, head of trading at Keefe, Bruyette & Woods in New York.
The Russell 2000 index of smallcap stocks was down 2.13 percent, on pace for its worst day since September.
The financial sector has been the best performing of the 11 major S&P sectors since Trump's election, surging nearly 20 percent on his proposals to cut bank regulations and reduce taxes.
The Dow Jones Industrial Average was down 0.97 percent at 20,702.71 points, while the S&P 500 lost 1.05 percent to 2,348.52.
The Nasdaq Composite dropped 1.49 percent to 5,813.39.
The CBOE Volatility index, Wall Street's "fear gauge", jumped 7 percent.
Under Trump, Wall Street has become unaccustomed to steep selloffs. The last time the S&P 500 lost 1 percent or more in a day was 110 trading sessions ago on October 11. Over the past two years, the S&P 500 has suffered losses of 1-percent or more about once every 11 sessions, according to Thomson Reuters data.
But investors have grown concerned about elevated valuations. The S&P 500 is trading at about 18 times forward earnings estimates against the long-term average of 15, according to Thomson Reuters data.
Declining issues outnumbered advancing ones on the NYSE by a 3.68-to-1 ratio; on Nasdaq, a 4.48-to-1 ratio favored decliners.
The S&P 500 posted 26 new 52-week highs and 7 new lows; the Nasdaq Composite recorded 73 new highs and 69 new lows.
Additional reporting by Chuck Mikolajczak and Sinead Carew in New York, editing by Nick Zieminski