* S&P 500 has struggled to close over 100-day moving average
* Energy to be in focus with Syria situation uncertain
* H&R Block posts wider-than-expected quarterly loss
* Dow down 20 pts, S&P down 1.4 pt, Nasdaq up 6.75 pts
By Ryan Vlastelica
NEW YORK, Sept 4 (Reuters) - U.S. stock index futures pointed to a mostly flat open on Wednesday as a Western military strike against Syria appeared more likely, though a decision remained several days away.
The odds for military action had appeared to ebb over the weekend after U.S. President Barack Obama said he would seek Congressional authorization for a strike. While Congress won't vote until it returns from its summer recess on Sept. 9, key congressional figures back the plan, suggesting approval may be more likely.
Secretary of State John Kerry said any resolution approving military force would prohibit "boots on the ground," comments that indicated that a strike would be limited in scope.
"I think a relatively minor strike is now built into the market. If the scope changes and we start talking about regime change, the market will have to adjust again to that," said John Brady, managing director at R.J. O'Brien & Associates in Chicago.
"Until we get more clarity on the geopolitical news, I suspect we'll continue trading in a tight range."
Uncertainty over Syria and concern over the economic impact of any Western-led action have been the market's primary drivers over the past week. Energy has been the most impacted, with crude rising 1.6 percent over the past two weeks as investors bet a Middle East engagement would limit oil supplies.
Adding to concern overseas, Italian shares slumped on worries over the survival of the country's government. European shares lost 0.4 percent.
S&P 500 futures fell 1.4 point and were slightly under fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures slid 20 points and Nasdaq 100 futures rose 6.75 points.
On the S&P 500, investors will be watching the 1,639.88 level, the index's 100-day moving average. The index has risen above that level in each of the past four sessions, though it hasn't closed above it since Aug. 26, a sign that near-term momentum continues to stall.
In company news, Rochester Medical Inc jumped 44 percent to $19.87 in premarket trading after C.R. Bard Inc agreed to buy the company for $262 million.
H&R Block Inc reported an adjusted quarterly loss Tuesday that was wider than expected, citing higher costs. Shares fell 4.1 percent to $26.75 in premarket trading.
Dollar General Corp shares rose 3.9 percent to $56 in premarket trading after reporting results that topped expectations, while SAIC Inc fell 4.4 percent to $14.49 after its results.
Hain Celestial Group Inc shares will be in focus a day after the company said activist investor Carl Icahn and his entities were cutting their stake in the company by roughly half.
The U.S. trade deficit widened slightly more than expected in July as exports dipped, but a rebound in imports pointed to some firming in underlying demand early in the third quarter.
Investors await the release of the U.S. Federal Reserve's Beige Book summary of economic conditions at 2:00 p.m. The report will be scoured for insight into when the central bank will begin to slow its accommodative monetary policies, which have fueled the equity market's gains in 2013.
Wall Street rose on Tuesday, but pared its gains in afternoon trading as key figures in Congress announced support for military action against Syria.