* Global stocks gain for a 2nd straight day
* Oil prices spike on Iran sanctions
* Trade concerns keep pressure on emerging mkts (Updates to midday U.S. trading)
By Trevor Hunnicutt
NEW YORK, Sept 11 (Reuters) - A broad index of world stock markets posted gains for a second straight day, as investors swooned over U.S. technology and energy stocks even as a trade war loomed.
MSCI's index of global equities gained 0.13 percent as investors awaited action from U.S. President Donald Trump after a deadline for public comment on additional tariffs ,on Chinese goods expired.
Wall Street continued to climb, with the benchmark S&P 500 stock index still on pace to deliver what once seemed improbable: a 7th year of double-digit percentage gains over the last decade.
Shares of Apple Inc surged 2.2 percent, a day ahead of the highly anticipated unveiling of the company's new iPhone models. Energy stocks got a boost from an oil market rally. U.S. markets may see more stimulus this year from additional tax cuts being pondered by congressional Republicans.
The Dow Jones Industrial Average rose 138.48 points, or 0.54 percent, to 25,995.55, the S&P 500 gained 10.82 points, or 0.38 percent, to 2,887.95 and the Nasdaq Composite added 32.88 points, or 0.41 percent, to 7,957.04.
"The fact that Trump still hasn't announced the tariffs yet as expected has prompted a bit of cautious optimism, but it's not a problem that's going to go away," said CMC Markets analyst Michael Hewson.
Emerging markets remained under pressure, with an index of those countries' shares down 0.82 percent. Those markets' currencies are at their lowest level in more than a year, with some near record lows against the U.S. dollar. Copper, heavily consumed by emerging markets, lost 0.53 percent to $5,878.50 a tonne.
China told the World Trade Organization (WTO) on Tuesday it wanted to impose $7 billion a year in sanctions on the United States in retaliation for Washington's non-compliance with a ruling in a dispute over U.S. dumping duties.
Having warned last week that he was ready to slap additional taxes on practically all Chinese imports, Trump has been uncharacteristically quiet on trade this week. U.S. trade talks with Canada are also ongoing.
"Weakness is set to remain a recurring theme amid global trade tensions, a broadly stronger dollar and prospects of higher U.S. interest rates," said Lukman Otunuga, a research analyst at broker FXTM.
"With turmoil in Turkey and Argentina triggering contagion fears, appetite for emerging market assets and currencies is likely to continue diminishing."
Oil prices ignored the threat to demand posed by a trade war that could slow economic growth, instead taking their cue from looming U.S. sanctions against Iran's petroleum industry that could hurt supply.
U.S. crude futures climbed 2.8 percent to $69.43 per barrel and Brent was last at $79.17, up 2.33 percent on the day.
Bond markets prepared to digest $144 billion in new supply from government auctions needed to finance U.S. deficit spending. Benchmark 10-year notes last fell 11/32 in price to yield 2.9755 percent, from 2.937 percent late on Monday.
Reporting by Trevor Hunnicutt; Additional reporting by Abhinav Ramnarayan in London; Editing by Bernadette Baum