US STOCKS-Wall Street treads water ahead of Trump's tariff decision

* Trump to make announcement on tariffs later today

* Express Scripts jumps after Cigna's $53 bln bid

* Dow down 0.18 pct, S&P up 0.04 pct, Nasdaq up 0.23 pct(Updates to early afternoon)

By Sruthi Shankar

March 8 (Reuters) - U.S. stock indexes traded in a narrowrange on Thursday as investors digested President Donald Trump'slatest comments on his proposed hefty metal tariffs ahead of anannouncement late afternoon.

Trump said he would initially stick with the 25 percentduties on steel imports and 10 percent on aluminum and that hehad a right to drop out countries or add countries, creatinguncertainty among market participants.

Trump, who is expected to proclaim the tariffs at 03:30 p.mET, promised Canada and Mexico would likely be exempted from thetariffs if they agree on a trade deal with the United States.

"As has been in the past, what President Trump says and whatfinally actually materializes are two different things," saidRandy Frederick, vice president of trading and derivatives forCharles Schwab in Austin, Texas.

"It might be just wise to sit on the sidelines before we getsome more clarity."

At 12:41 p.m. ET, the Dow Jones Industrial Averagewas down 0.18 percent at 24,755.82.

The S&P 500 was up just 0.04 percent to 2,727.98 andthe Nasdaq Composite rose 0.23 percent to 7,413.77.

Worries over the likelihood of a global trade war triggeredby Trump's tariff plans have dominated markets since lastThursday, with Trump's chief economic adviser Gary Cohn's exitheightening such concerns.

The plan has faced with strong opposition from most of keypartners, with Europe and China warning they would respond inthe event of a trade war with the United States.

"If he (Trump) does announce much more draconian measuresthat are going to knock on to other products, I think there willbe a sell-off," said Dec Mullarkey, managing director at SunLife Investment Management based in Wellesley, Massachusetts.

Express Scripts was among the top boosts to the S&P500, rising 9.4 percent after health insurer Cigna agreedto buy the pharmacy benefits manager for almost $53 billion.Cigna shares slipped 11.2 percent.

Kroger fell more than 10 percent after thesupermarket chain issued a disappointing full-year profitforecast.

American Eagle Outfitters turned 8 percent lowerafter trading up premarket on concerns over falling margins.

Declining issues outnumbered advancers on the NYSE by 1,502to 1,318. On the Nasdaq, 1,467 issues fell and 1,365 advanced.

(Reporting by Sruthi Shankar in Bengaluru; Editing by SrirajKalluvila)