By Alexandra Scaggs 

U.S. stocks drifted around unchanged levels midday, pausing after the S&P 500 index closed above 2000 for the first time.

The Dow Jones Industrial Average tacked on 11 points, or 0.1%, to 17117. The S&P 500 index rose less than 0.1% to 2000, and the Nasdaq Composite Index edged up less than 0.1% to 4572.

Stocks drifted between slight gains and losses after Tuesday's quiet trading session, when the S&P 500 made its 30th record close for the year and the Dow hit a fresh intraday high.

There was little economic news on the calendar Wednesday, so traders instead eyed the latest news on high-profile deals. Broadly, a rising level of deals activity has helped support the U.S. stock market this year, say investors and strategists. Paul Karos, senior portfolio manager with Whitebox Mutual Funds, said that he is buying shares of some companies that could attract activist investors' involvement.

"Deals activity is likely to continue," said Mr. Karos, who helps manage $100 million in the Whitebox Market Neutral Equity Fund. "So we're looking for names where there are strong fundamentals, and where there might be activist potential."

A deal for Burger King Worldwide to buy Tim Hortons Inc., backed by investor Warren Buffett, came under criticism. The deal would allow the hamburger chain to move its headquarters to Canada in a so-called tax inversion. Shares of Burger King fell 3.4%, and shares of Tim Hortons shed 1.6%.

Chinese e-commerce giant Alibaba Group filed fresh financial results ahead of its initial public offering, which is expected next month. Yahoo Inc., which owns a chunk of the company, gained 0.7%.

"The Alibaba IPO is going to be enormous for Wall Street," said Michael Purves, chief global strategist for Greenwich, Conn.-based brokerage firm Weeden Co.

The Dow has gained 3.2% and the S&P 500 is up 8.2% for the year, through Tuesday's close. The S&P 500 has recovered from a mid-July swoon, caused in part by a flare-up in concerns about Ukraine and the Middle East. The Dow isn't far behind, hovering 0.2% below its July 16 record as of Tuesday's close.

Treasury prices continued to push higher, with the yield on the 10-year note remaining near its lowest level since June 2013. In recent trading, the yield on the benchmark 10-year note fell to 2.371%, according to FactSet.

European stocks were mixed, with the Stoxx Europe 600 edging up 0.1%. Expectations for further easing from the European Central Bank have been building in the wake of continued weak economic data and remarks from ECB President Mario Draghi last week.

In other corporate news, Tiffany Co. rose 1% after it reported better-than-expected second-quarter results and lifted its earnings outlook for the year.

In commodity markets, crude-oil futures fell 0.4% to $93.53 a barrel. Gold futures slipped 0.2% to $1,283.20 an ounce.

Write to Alexandra Scaggs at alexandra.scaggs@wsj.com