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Global share prices retreated to their lowest levels since early July on Friday after two weeks of relentless losses dominated by uncertainty about the outcome of the U.S. presidential election and, as of Thursday, Britain's path out of the European Union.

A London High Court ruling on Thursday dealt a big blow to Prime Minister Theresa May's plans to launch formal Brexit talks next March, prompting speculation of an early national election and sending sterling spinning higher.

The dollar at the same time has been hammered by a surge for U.S. Republican presidential candidate Donald Trump in opinion polls in the past week. Investors believe this may prevent the U.S. Federal Reserve from raising interest rates next month.

Republican presidential nominee Donald Trump holds a campaign event in Pensacola, Florida, on November 2, 2016. CARLO ALLEGRI / Reuters

Broader jitters about the shape of global trade and growth under a Trump presidency have also helped send shares down across the globe, and the major markets in Europe and Asia were all again in retreat on Friday.

MSCI's global share index slipped just under half a percent to its lowest since July 11 and is down almost 5 percent over the past two weeks.

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"With only a few days left until Americans go to the polls many traders are continuing to reduce their risk exposure further," said Markus Huber, a trader with brokers City of London Markets.

Stock markets in Germany, Spain, France, and Italy all fell around 1 percent.

MSCI's broadest index of Asia-Pacific shares outside Japan slipped 0.4 percent after brushing its lowest levels since early August. It looked set for a loss of 1.7 percent for the week.

The latest polling showed Clinton, seen as the status quo candidate by markets, maintaining a narrow lead over Trump. But several swing states that the Republican challenger must win have shifted from favoring Clinton to toss-ups, offering Trump a possible route to victory.

"Even if opinion polls show that Clinton is maintaining a lead, anything can happen at the last minute, something the Brexit (referendum) outcome taught us," said Norihiro Fujito, senior investment strategist at Mitsubishi UFJ Morgan Stanley Securities.

With only a few days left until Americans go to the polls, many traders are continuing to reduce their risk exposure further.

In his campaign Trump, a political novice, has vowed to clamp down on immigration, rethink trade relations and slap high tariffs on imported goods.

U.S. stocks sagged on Thursday, with the S&P 500 suffering its eighth day of losses, its longest streak since the 2008 financial crisis. A slump in Facebook shares also sapped investor confidence.

The dollar clawed back some lost ground against the yen in Europe on Friday, rising 0.2 percent to 103.19 , but was still on course for a 1.5 percent loss for the week.

The euro edged down 0.1 percent to $1.1097, up about 1 percent for the week.

Attention will move at least briefly to the monthly U.S. nonfarm payrolls report later on Friday, the addition of 175,000 jobs by employers in October expected to lay the economic ground for a Fed rate rise next month.