The financial index .SPSY dropped 2 percent and was on track for the biggest daily percentage fall since January 17.
"If that comes to fruition, that would be a huge plus", said Peter Cardillo, chief market economist at First Standard Financial.
Benchmark 10-year U.S. Treasuries rose 11/32 in price to yield 2.43 percent, the lowest yield since March 1.
Some investors fear that if the healthcare reform act runs into trouble or takes longer-than-expected to pass, then Trump's tax reform policies may face setbacks.
Five of the 11 major S&P sectors were lower, with the financial index's 1.32 percent fall leading the decliners.
His unsubstantiated tweet distracted from the claims of Russian interference in the election - as well as efforts by Republicans to push through a healthcare overhaul. The central bank raised rates by 25 basis points but signaled it would remain on a gradual pace of hike.
"Market participants are anxious about the effects and feasibility of Donald Trump's growth programme", DZ Bank strategist Birgit Figge said.
Microsoft Surface Phone launch delayed, software not ready
That includes a new super-charged version - the Surface Book with Performance Base - which was launched in the fall of 2016. The new Surface Book entered mass production recently, says , with shipments expected to rise each month.
The financial sector has been the best performing of the 11 major S&P sectors since Trump's election, surging almost 20 percent on his proposals to cut bank regulations and reduce taxes.
Investors have grown concerned about elevated valuations, with stocks hovering near record highs for most of the month.
Winners beat losers by a 6-5 ratio on the NYSE and Nasdaq.
At 9:41 a.m., the Toronto Stock Exchange's S&P/TSX composite index fell 45.28 points, or 0.3 per cent, to 15,267.85.
US -listed shares of Deutsche Bank fell 2.8 percent to $18.50 after the German lender disclosed terms of its almost $9 billion cash call.
The S&P 500 index showed eight new 52-week highs and no new lows, while the Nasdaq recorded 32 new highs and 11 new lows.