* Yellen to speak on Friday, no new policy view expected
* Dollar Tree, Signet rise on strong earnings reports
* Hormel, JM Smucker fall after disappointing results
* Oil slips 1.75 pct as dollar gains ahead of Jackson Hole
* Indexes down: Dow 0.06 pct, S&P 0.14 pct, Nasdaq 0.29 pct (Updates to early afternoon)
Aug 24 (Reuters) - U.S. stocks were mostly lower in early afternoon trading on Thursday, with investors cautious as they await comments on monetary policy from central bankers gathered for their annual meet in Jackson Hole, Wyoming.
Speeches from Federal Reserve Chair Janet Yellen and European Central Bank President Mario Draghi on Friday will be scrutinized for hints on the path of monetary policy, but neither of them are expected to give fresh guidance.
The central bankers' views will be a change from the past two weeks, when the stock market was roiled by concerns over geopolitics, mayhem in Washington, and President Donald Trump's controversial comments.
Trump on Wednesday threatened to shut down the government if funds were not secured to build a Mexico border wall, comments that came as a late-September deadline looms for U.S. officials to raise the debt ceiling or risk a default.
"Political uncertainties remain ongoing, valuations are full and, technically, there is some signs of deterioration (in the stock market)," said Terry Sandven, chief equity strategist at U.S. Bank Wealth Management in Minneapolis.
"The backdrop seems favorable for equities to do what we're seeing this morning and that is sideways trending."
At 12:40 p.m. ET (1640 GMT), the Dow Jones Industrial Average was down 13.83 points, or 0.06 percent, at 21,798.26 and the S&P 500 was down 3.38 points, or 0.14 percent, at 2,440.66.
The Nasdaq Composite was down 18.40 points, or 0.29 percent, at 6,260.01.
Oil prices slipped about 1.75 percent as the dollar strengthened ahead of the Jackson Hole meeting.
Seven of the 11 major S&P sectors were lower, led by a 0.55 percent drop in the consumer staples index.
Shares of Dollar Tree rose more than 10 percent, on course to record its best day in more than a year, after the retailer reported profit and comparable sales that beat estimates.
Signet Jewelers surged about 20 percent after the company issued its results and said it would buy an online jeweler.
While these two stocks were the top percentage gainers on the S&P, Hormel Foods and J.M. Smucker brought up the rear, falling about 6 percent and 7.5 percent, respectively, after their weak quarterly results and forecast cuts.
Even economic data on the day was a mixed bag: while the number of Americans filing for unemployment benefits rose less than expected last week, home resales unexpectedly fell in July to their lowest monthly level of the year.
Advancing issues outnumbered decliners on the NYSE by 1,597 to 1,154. On the Nasdaq, 1,614 issues rose and 1,141 fell. (Reporting by Sruthi Shankar in Bengaluru; Editing by Savio D'Souza)