* Oil jumps, energy stocks top gainers on S&P 500
* Micron sinks on pricing worries, weighs on chip stocks
* Dropbox surges as much as 50 pct in trading debut
* Indexes down: Dow 0.21 pct, S&P 0.45 pct, Nasdaq 0.71 pct (Updates to early afternoon)
By Sruthi Shankar
March 23 (Reuters) - Wall Street on Friday struggled to shake off fears of a global trade war after the United States moved to slap tariffs on China and as technology stocks took another hit with Micron's results weighing on chipmakers, though oil prices gave some succor.
The Dow Jones Industrial Average and the benchmark S&P 500 indexes swung between gains and losses in a choppy session, but the Nasdaq Composite stayed firmly in the red. The three indexes are on track for their biggest weekly declines in six weeks.
After President Donald Trump announced tariffs on up to $60 billion of Chinese goods, Beijing disclosed plans for tariffs on up to $3 billion of U.S. imports, though it also urged the United States to "pull back from the brink."
"There's a little bit of nervousness out of Washington now. Investors are more content to be at the sidelines over the next couple of weeks as we see what develops on the trade war," said said RJ Grant head of trading at Keefe, Bruyette & Woods in New York.
"It's prudent to take a little off the table."
Micron Technology reported better-than-expected quarterly results, but the stock fell 6.5 percent after its report showed deteriorating NAND prices.
That sparked a tumble in other chipmakers, sending the Philadelphia semiconductor index down 1.8 percent. The S&P tech index, already under pressure this week in the wake of the Facebook data scandal, fell 0.99 percent.
At 12:36 p.m. ET, the Dow Jones Industrial Average was down 0.21 percent at 23,908.01. The S&P 500 fell 0.45 percent to 2,631.83 and the Nasdaq Composite dropped 0.71 percent to 7,115.47.
The S&P energy index was up 0.78 percent, with oil prices gaining and providing some relief to the market, as they have for most of this week.
Oil prices jumped about 1.5 percent after the Saudi energy minister said OPEC and allied producers would need to keep coordinating supply cuts into 2019.
Nike rose more than 2.3 percent after the company said it expected North America business to return to growth in the latter half of the year.
One bright spot among tech stocks was Dropbox Inc, which surged as much as 50 percent in its trading debut. The stock was last up 41 percent at $29.63 in heavy trading on heavy demand for the biggest tech IPO in over a year.
Declining issues outnumbered advancers on the NYSE for a 1.49-to-1, and for a 1.90-to-1 ratio on the Nasdaq. (Reporting by Sruthi Shankar in Bengaluru, additional reporting by Sinead Carew in New York; Editing by Savio D'Souza)