(Jan 18): The Dow Jones Industrial Average was lower for the fourth straight trading day on Wednesday, while the S&P 500 and the Nasdaq were little changed, ahead of Federal Reserve Chair Janet Yellen's speech.

Investors are also awaiting President-elect Donald Trump's inaugural speech on Friday to gain more insight into his plans for the US economy.

The Trump rally, which drove Wall Street to record highs, has been showing signs of fatigue since the start of the year as investors get increasingly nervous about his unconventional approach to trade and politics.

"There is a lot of uncertainty hovering over the market, regarding what policies will be implemented," said Quincy Krosby, market strategist at Prudential Financial.

"But the market appears to be giving the President-elect the benefit of the doubt."

At 9:45am ET the Dow Jones industrial average was down 41.37 points, or 0.21%, at 19,785.4. The S&P 500 was down 0.27 points, or 0.01%, at 2,267.62, while the Nasdaq Composite was up 7.16 points, or 0.13%, at 5,545.89.

Six of the 11 major S&P 500 sector indexes were lower, with consumer discretionary and energy the big losers.

UnitedHealth fell 2.4% to US$156.93 and was the biggest drag on the Dow.

Target dropped 5.2% after the big-box retailer reported a decline in sales during the holiday season and cut its fourth-quarter earnings forecast. Shares of bigger rival Wal-Mart were off about 1%.

A report from the US Labor Department showed the Consumer Price Index edged up 0.3% in December, leading to the largest year-on-year increase in 2-1/2 years, a sign that inflation pressures could be building.

Investors will watch Janet Yellen's speech to see if she will echo a growing opinion among policymakers that fiscal stimulus under the Trump administration may call for more aggressive interest rate hikes.

Declining issues outnumbered advancers on the NYSE by 1,418 to 1,178. On the Nasdaq, 1,257 issues rose and 1,081 fell.

The S&P 500 index showed four new 52-week highs and two new lows, while the Nasdaq recorded 22 new highs and 10 new lows.