* Vote on legislation set for 3:30 pm ET, White House says
* S&P 500 on track for biggest weekly decline of the year
* Micron jumps after forecasts beat estimates, helps Nasdaq
* Dow down 0.13 pct, S&P up 0.05 pct, Nasdaq up 0.32 pct (Updates to late afternoon)
By Lewis Krauskopf
March 24 (Reuters) - U.S. stocks edged up in choppy trading on Friday as investors braced for the outcome of a vote on a healthcare bill and considered how its potential failure might affect President Donald Trump's broader economic agenda.
Trump's fellow Republicans in Congress said they lacked the votes needed for passage of their bill to overhaul the U.S. healthcare system and replace the law known as Obamacare. The vote was scheduled for 3:30 p.m. EDT/1930 GMT, according to the White House.
The back-and-forth over the bill has led to some of the most volatile trading Wall Street has seen since Trump's election in November and has set the benchmark S&P 500 on course for its worst weekly decline of the year.
Investors have worried that a failure of the legislation would damage prospects for Trump's agenda, including tax reform, infrastructure spending and deregulation. Earlier this week, on Tuesday, U.S. stocks posted their biggest daily drop since the election.
Some of that concern appeared to be ebbing on Friday ahead of the scheduled vote in the House, with some analysts and investors seeing a failure of the bill as a catalyst to bring forward action on tax reform in particular.
"Investors are coming to the conclusion that either way the vote goes or if they delay it further, that they will start working on the rest of the Trump agenda, and that’s what investors are interested in," said Alan Lancz, president of investment advisory firm Alan B. Lancz & Associates in Toledo, Ohio.
The Dow Jones Industrial Average fell 27.66 points, or 0.13 percent, to 20,628.92, the S&P 500 gained 1.1 points, or 0.05 percent, to 2,347.06 and the Nasdaq Composite added 18.61 points, or 0.32 percent, to 5,836.30.
The S&P 500 has climbed about 10 percent since Trump's election, notching a series of record highs along the way. But the rally has stalled recently, and Tuesday's 1.2 percent drop set off concerns about the beginning of a larger drop.
"The economy and earnings were doing better since before the election," said Paul Zemsky, chief investment officer for multi-asset strategies and solutions at Voya Investment Management in New York. "If people want to drop the S&P by 300 points because this doesn’t pass, I and others will be down there to buy it."
In corporate news, Micron Technology jumped 8.7 percent after the chipmaker's revenue and profit forecasts beat expectations. The stock was the biggest percentage gainer on the S&P and helped lift the Nasdaq.
GameStop tumbled 12.3 percent after the company's profit projection fell below estimates.
Advancing issues outnumbered declining ones on the NYSE by a 1.52-to-1 ratio; on Nasdaq, a 1.53-to-1 ratio favored advancers.
The S&P 500 posted 19 new 52-week highs and 1 new lows; the Nasdaq Composite recorded 56 new highs and 28 new lows. (Additional reporting by Rodrigo Campos in New York and Tanya Agrawal in Bengaluru; Editing by Anil D'Silva and Nick Zieminski)