Materials sector shares led the advance, with DuPont up 4.4 percent at $68.72 after activist investor Nelson Peltz's Trian Fund Management, among the biggest shareholders in the company, urged it to separate its high-growth businesses from those with strong cash flows.
The broader market had its eyes on the Fed as it concludes a two-day policy meeting. It is expected to provide indications on how soon it may lift interest rates as it prepares for a shift in stance after years of aggressive monetary stimulus.
The benchmark S&P 500 posted its best daily performance in a month Tuesday and the Dow industrials set a record intraday high amid wavering expectations regarding the Fed's stance.
Tuesday's rally "discounted a favorable Fed statement today so anything more hawkish than a statement very close to the last one will probably be read negatively," said Jack De Gan, chief investment officer at Harbor Advisory Corp in Portsmouth, New Hampshire.
He said if the statement was supportive of equities, the S&P should test resistance near the 2,010 area.
The Dow Jones industrial average was rising 28.87 points, or 0.17 percent, to 17,160.84, the S&P 500 was gaining 3.71 points, or 0.19 percent, to 2,002.69 and the Nasdaq Composite was adding 3.82 points, or 0.08 percent, to 4,556.58.
The largest percentage gainer on the New York Stock Exchange was U.S. Steel, which jumped 9.86 percent a day after the company estimated its results to be "significantly" higher than current Wall Street estimates. The largest decliner was Rackspace Hosting, down 15.98 percent after the cloud management services provider said it would not sell itself.
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Among the most active stocks on the NYSE were Civitas Solutions, down 1.47 percent to $16.75; Petrobras, up 2.57 percent to $17.96 and Alcoa Inc, up 0.19 percent to $16.19.
On the Nasdaq, Net Element Inc, up 34.2 percent to $3.49; TiVo INC, down 1.1 percent to $13.56 and Yahoo , down 0.5 percent to $42.50, were among most active.
Net Element announced it will make it possible for customers to use Apple Pay by integrating Apple services into its point-of-sale payment acceptance hardware and software.
Advancing issues were outnumbering declining ones on the NYSE by 1,917 to 813, for a 2.36-to-1 ratio; on the Nasdaq, 1,419 issues were rising and 814 falling for a 1.74-to-1 ratio.
The broad S&P 500 index was posting 30 new 52-week highs and 5 new lows; the Nasdaq Composite was recording 24 new highs and 19 new lows.
(Editing by Bernadette Baum)