* Trump fires chief strategist Steve Bannon
* Nike, footwear retailers trampled as price war sparks concerns
* All three indexes post losses for the week
* Indexes: Dow down 0.4 pct, S&P down 0.2 pct, Nasdaq down 0.1 pct (Adds details on recent stocks decline)
By Caroline Valetkevitch
NEW YORK, Aug 18 (Reuters) - U.S. stocks lost ground late to end lower on Friday following a White House-focused week that raised more questions about the Trump administration's ability to implement its pro-growth agenda.
While the day's losses were small, Friday marked the first time stocks haven't risen the day after a more than 1 percent drop since Donald Trump was elected president on Nov. 8.
The week's losses further dented the post-election rally, which was built on Trump's promises of tax cuts and higher infrastructure spending.
Thursday's 1.5-percent drop in the S&P 500 came a week after a similar fall, and while the benchmark index still is up 13.4 percent since the election, it is down 2.1 percent in the last two weeks. That's the most since the two weeks before the election.
"While this mini correction we're seeing may not amount to much, it's probably caused by this escalation in doubt of all of these things that seemed hopeful to investors at the beginning of the Trump administration," said J. Bryant Evan, investment advisor and portfolio manager at Cozad Asset Management, in Champaign, Illinois.
In the latest shakeup, the White House said Trump on Friday fired chief strategist Steve Bannon, known as an economic nationalist and an advocate of "America First" policies. Critics have accused him of harboring anti-Semitic and white nationalist sentiments.
While stocks turned higher following reports of Bannon's departure, they lost those gains heading into the close.
The news followed a week heavy with speculation and focus on the White House. On Thursday, there was concern about the possible departure of National Economic Council Director Gary Cohn; on Wednesday, Trump disbanded some business councils.
Trump also alienated some corporate leaders and U.S. allies this week with his comments following violence in Charlottesville, Virginia, where there was a white nationalist protest against the removal of a Confederate statue.
The Dow Jones Industrial Average fell 76.22 points, or 0.35 percent, to close at 21,674.51, the S&P 500 lost 4.46 points, or 0.18 percent, to 2,425.55 and the Nasdaq Composite dropped 5.39 points, or 0.09 percent, to 6,216.53.
The S&P 500 closed roughly 1 percent below its 50-day moving average, the furthest below that key technical measure since mid-April and the closest to its 200-day moving average since the election.
For the week, the Dow was down 0.8 percent, the S&P 500 was down 0.7 percent and the Nasdaq fell 0.6 percent.
Shares of sporting goods retailers and Deere weighed on the market following disappointing results.
Nike's 4.4-percent slide weighed the most on the Dow, following dismal results from sporting goods retailers Foot Locker and Hibbett.
Deere's 5.4-percent fall was the biggest drag on the industrial sector after the farm equipment maker reported a second straight quarter of lower-than-expected sales.
Friday also was the eighth straight day in which the New York Stock Exchange and Nasdaq had more stocks making new 52-week lows than highs, matching a similar streak leading up to Trump's election.
About 290 issues hit a 52-week low on Friday, the most since immediately after the presidential vote.
The market's rally faces further tests in the weeks ahead with the approach of a historically weak month for equities and a host of other issues that could weigh on market, including the Federal Reserve's September meeting, where it could announce plans to unwind its bond portfolio.
Advancing issues outnumbered declining ones on the NYSE by a 1.12-to-1 ratio; on Nasdaq, a 1.04-to-1 ratio favored advancers.
About 6.8 billion shares changed hands on U.S. exchanges. That compares with the 6.4 billion daily average for the past 20 trading days, according to Thomson Reuters data. (Additional reporting by Sruthi Shankar and Tanya Agrawal in Bengaluru; Editing by Nick Zieminski and James Dalgleish)