* Trump to make announcement on tariffs later today
* Express Scripts jumps after Cigna's $54 bln offer
* Real estate, healthcare stocks lead advancers
* Dow down 0.12 pct, S&P up 0.01 pct, Nasdaq up 0.2 pct (Changes comment, adds details, updates prices)
By Sruthi Shankar
March 8 (Reuters) - U.S. stocks gave up earlier gains on Thursday ahead of President Donald Trump's announcement of his hefty metals tariffs amid easing concerns that the move could ignite a global trade war.
Trump, who is expected to sign a proclamation imposing tariffs at 03:30 p.m ET, promised Canada and Mexico would likely be exempted from the tariffs on steel and aluminum imports if they agree on a trade deal with the United States.
Trump also said he was sticking with 25 percent tariffs on steel and 10 percent on aluminum.
"As has been in the past, what President Trump says and what finally actually materializes are two different things," said Randy Frederick, vice president of trading and derivatives for Charles Schwab in Austin, Texas.
"It might be just wise to sit on the sidelines before we get some more clarity."
At 11:45 a.m. ET, the Dow Jones Industrial Average was down 28.9 points, or 0.12 percent, at 24,772.46, the S&P 500 was up 0.3 points, or 0.011 percent, at 2,727.1.
The Nasdaq Composite was up 14.91 points, or 0.2 percent, at 7,411.55.
Worries over the likelihood of a global trade war triggered by Trump's tariff plans have dominated markets since last Thursday, with chief economic adviser Gary Cohn's exit heightening such concerns.
The plan has faced with strong opposition from most of key partners, with Europe and China warning they would respond in the event of a trade war with the United States.
"If he (Trump) does announce much more draconian measures that are going to knock onto other products, I think there will be a sell-off," said Dec Mullarkey, managing director at Sun Life Investment Management based in Wellesley, MA.
Express Scripts was among the top boosts to the S&P 500, rising 12 percent after health insurer Cigna agreed to buy the pharmacy benefits manager for $54-billion deal. Cigna shares slipped 7.6 percent.
The deal boosted the S&P healthcare index, up 0.55 percent. Real estate also rose 0.62 percent.
Kroger fell more than 10 percent after the supermarket chain issued a disappointing full-year profit forecast.
American Eagle Outfitters turned 9.8 percent lower after trading up premarket on strong results.
Declining issues outnumbered advancers on the NYSE by 1,381 to 1,322. On the Nasdaq, 1,380 issues fell and 1,328 advanced. (Reporting by Sruthi Shankar in Bengaluru; Editing by Sriraj Kalluvila)