* MSCI world index unlikely to hit best streak since 2003
* Asia-Pac index near 10-yr high, Nikkei lurches after high
* Tax plan worries weigh on dollar, U.S. stocks
* Crude oil steadies, gold hovers near 3-week high
* Bitcoin slides 5 percent after latest record high (Updates with U.S. mid-day trading)
By David Randall
NEW YORK, Nov 9 (Reuters) - Broad equity market declines in Asia and Europe on Thursday, combined with growing concerns that the Republican-led corporate U.S. tax cut may not pass this year, threatened to spoil the longest winning streak for MSCI's global stock index since 2003.
Wall Street stocks opened lower [.N ]and added to their losses after Republican Sen. Bill Cassidy, a member of the Senate Finance Committee, said that the Senate tax proposal will delay a corporate tax cut by one year to 2019.
The Dow Jones Industrial Average fell 211.64 points, or 0.9 percent, to 23,351.72, the S&P 500 lost 23.38 points, or 0.90 percent, to 2,571 and the Nasdaq Composite dropped 87.43 points, or 1.29 percent, to 6,701.69.
"The stock market has run out of a little momentum," said Societe Generale strategist Kit Juckes. "We are waiting for some news from the Republicans on the (U.S.) tax plans, there is a bond market that has stalled and we've got rather soggy-looking emerging markets... We probably need to get U.S. Treasury yields higher to get things going again."
Japan’s Nikkei index swung by a wild 2 percent after hitting its highest since 1992 and Europe's main indexes were firmly in the red as tech and commodity stocks tumbled while Brexit talks resumed amid low expectations in Brussels.
MSCI's all-country equity index is clocking year-to-date gains of almost 19 percent. (reut.rs/1WAiOSC)
But as a measure of relative calm amid the current bull market and a reflection of the low volatility environment that has dominated all year, none of the most recent 10 daily gains has exceeded half a percent and more than half of them were less than 0.1 percent.
The dollar index, which tracks the greenback versus a basket of six key currencies, fell 0.378 points or 0.4 percent, to 94.488.
"There's very much a risk of disappointment. The U.S. dollar could go through a weakening phase on the back of uncertainty around that tax reform," said Steven Dooley, currency strategist for Western Union Business Solutions in Melbourne.
Some also focused on fallout from Democrat wins in regional U.S. elections this week as a signal for next year’s mid-term congressional elections for President Donald Trump.
Trump was in China on Thursday, pressing President Xi Jinping to do more to rein in North Korea and to open the Chinese economy - the second-biggest in the world after the United States - to more foreign firms.
The euro was last up 0.46 percent, at $1.1646, while Europe's broad FTSEurofirst 300 index dropped 1.09 percent at 1,534.88.
The pan-European FTSEurofirst 300 index lost 1.09 percent and MSCI's gauge of stocks across the globe shed 0.60 percent.
Oil prices steadied just below two-year highs, supported by supply cuts by major exporters, but analysts said the market could be vulnerable to a sell-off after several months of gains. U.S. crude rose 0.81 percent to $57.27 per barrel and Brent was last at $64.00, up 0.8 percent on the day.
Spot gold added 0.5 percent to $1,286.90 an ounce. U.S. gold futures gained 0.30 percent to $1,287.50 an ounce.
Cryptocurrency bitcoin skidded about 3 percent but not before dipping almost 5 percent.
It had hit a record high just shy of $8,000 on Wednesday after a coalition of developers and investors suspended a software upgrade planned for next Thursday that could have split the digital currency in two. (Additional reporting by Shinichi Saoshiro; Editing by Bernadette Baum and Dan Grebler)