(New throughout, updates prices and market activity to U.S. close)
* U.S. stocks slide almost 5%, halting Tuesday's rally
* BoE announces surprise 50 bps cut to tackle coronavirus shock
* Oil falls after Saudi Aramco announces more production
* Graphic: World FX rates in 2020 http://tmsnrt.rs/2egbfVh
By Herbert Lash
NEW YORK, March 11 (Reuters) - The dollar weakened and the Dow Jones industrials entered bear market territory on Wednesday on mounting worries about the global economy after world health officials declared a coronavirus pandemic and Reuters reported a White House gag order on top-level U.S. meetings on the outbreak.
Risk assets tumbled throughout the day, erasing more value from global stock markets that had already lost $8.1 trillion by Tuesday. Losses accelerated late in the session as the number of coronavirus cases increased and the United States weighed limits on travelers from Europe.
The World Health Organization's decision to label the outbreak a pandemic came as Britain and Italy announced multi-billion-dollar war chests to fight the disease.
Already skittish investors awaiting details on U.S. measures were unnerved by news that the White House ordered federal health officials to treat dozens of virus-related meetings as classified.
Government experts were among people without security clearance who were excluded from interagency meetings that restricted information and hampered the U.S. response to the contagion, four Trump administration officials told Reuters.
The WHO pandemic classification added to uncertainty in the market about the global economy. For the first time since the 2008 financial crisis, the Dow entered bear market territory, defined as a 20% decline from a recent peak. The S&P 500 and Nasdaq composite slid almost 6% at one point, also entering bear territory on an intraday basis although those losses were pared.
Kim Forrest, chief investment officer at Bokeh Capital Partners in Pittsburgh, said the classification pushed investors over the edge.
"We woke up really worried about it. There's a wider spread, the numbers are growing," she said. "I don't think anyone at this point knows the real scope of this."
Emotions drove the sell-off amid a negative backdrop of another emergency rate cut by a major central bank, the Bank of England, said Sal Arnuk, partner and co-founder of Themis Trading in Chatham, New Jersey. He said sentiment soured further on news the White House has classified coronavirus meeting information.
"If you feel the need to embargo information, a lot of people don't like that, because that makes you think they're concerned that the numbers are getting increasingly worse, so bad that they feel they need to shield the American public from that information," Arnuk said.
The Dow Jones Industrial Average fell 1,464.94 points, or 5.86%, to 23,553.22. The S&P 500 lost 140.85 points, or 4.89%, to 2,741.38 and the Nasdaq Composite dropped 392.20 points, or 4.7%, to 7,952.05.
Earlier in Europe, Tuesday's strong stock rally petered out. The BofE rate cut had investors pondering how much monetary and fiscal stimulus can dampen the epidemic's economic toll.
A gauge of long-term euro zone inflation expectations dropped to another record low. Analysts said this suggested investors were positioning for deflation risks.
Britain announced a $39 billion war chest to soften the impact of the coronavirus while Italy, the hardest hit country outside of China, said it might further tighten already draconian curbs.
European shares closed at a 14-month low as the benchmark STOXX 600 closed down 0.7%. MSCI's gauge of stocks across the globe shed 3.64%, close to bear territory.
Yields on U.S. Treasury debt rose in choppy trading despite the heavy stock losses. The benchmark 10-year note yielded 0.8313%.
The escalating coronavirus outbreak also has given the Federal Reserve a tough mission of trying to judge its potential economic impact in the absence of reliable data.
Economic stimulus will take time, while in the interim the virus will spread further and more businesses suspend their financial guidance, said Peter Tuz, president of Chase Investment Counsel in Charlottesville, Virginia.
Uncertainty has ramped up with no sign of abating, he said.
"The volatility due to the virus and the response to the virus is at very severe levels. I don't see it really calming down until our arms are around the number of people who are affected in the U.S.," he said.
More than 121,500 people have been infected globally and 4,383 have died, according to a Reuters tally of government announcements.
The dollar resumed its decline against the safe-haven Japanese yen and Swiss franc and gold rebounded, but was well off the $1,700 level it briefly hit Monday.
Sterling initially fell as much as 0.4% against the dollar and 1.2% against the euro after the BoE cut its benchmark rate by 50 basis points, to 0.25%.
The Japanese yen strengthened 1.00% versus the greenback at 104.61 per dollar.
Benchmark U.S. 10-year Treasury yields rose 5 basis points to yield 0.804%, more than double Monday's record low yield of 0.3180%.0.8711
German government bond yields rose after the BoE cut supported sentiment, while Italian yields -- which had shot up on worries the country with Europe's worst outbreak of the virus is sliding into a recession -- tumbled as much as 20 basis points as bets grew on ECB stimulus.
Oil prices fell about 4%, sinking into the close of trading on renewed weakness in the stock market and as Saudi Arabia and the United Arab Emirates announced plans to escalate the burgeoning price war.
Brent crude fell $1.43 to $35.79 a barrel, while U.S. West Texas Intermediate (WTI) crude fell $1.38 to settle at $32.98 a barrel.
(Reporting by Herbert Lash, additional reporting April Joyner in New York, Marc Jones in London; Editing by Catherine Evans and David Gregorio)