Global stocks traded modestly weaker Friday, pulling U.S. equity futures into the red and threatening the first five-day stretch of declines for the year, as investors reacted to reports of more White House turmoil and braced for news of new tariffs on China in the world's brewing trade war.

U.S. equity futures suggest a soft start to the trading session on Wall Street, as well, with contracts tied to the Dow Jones Industrial Average marked 12 points lower from Thursday's close, but still on pace to rise about 16 points at the opening bell while those linked to the broader S&P 500 seen 1.75 points to the upside after the benchmark fell for the fourth consecutive session last night.

Reports that special counsel Robert Mueller has subpoenaed documents from President Donald Trump's businesses that may have ties to Russia, along with speculation that National Security Adviser H.R. McMaster could be next to depart the White House, kept markets defensive overnight in Asia as investors plowed cash into the yen as a hedge against risk, taking the Japanese currency 0.61% higher against the U.S. dollar to 1.0568.

The move held down gains for the Nikkei 225 benchmark, which closed 0.58% lower at 21,676.51 points, although it still managed to book a one-week gain of just under 1%. The broader MSCI Asia ex-Japan index was marked 0.05% lower into  the close of the session.

European stocks were only slightly higher by mid-day in Frankfurt, with the Stoxx 600 index rising 0.08% to 377.31 points while Germany's DAX performance index gained 0.42% to 12,396 and Britain's FTSE 100 added 0.2% to 7,154.38.

Investors were also happy to move cash into U.S. Treasury bonds amid the White House turmoil, which has seen two key officials -- Secretary of State Rex Tillerson and chief economic adviser Gary Cohn -- leave the Trump team in as many weeks. Reports of the potential ouster of McMaster, denied by the White House, also come amid concern from some U.S. lawmakers that the recently-announced package of sanctions against a small number of Russian businesses and officials for cyber attacks and election tampering does't go far enough into the administration of President Vladimir Putin.

The dollar index, a measure of the greenback's strength against a basket of six global currencies, was marked 0.18% lower from Thursday's close at 89.98 during European trading, extending its year-to-date decline to 2.33%. Benchmark 10-year Treasury yields hit a four-week low of 2.797% last night before stablising at around 2.82% during European hours. Benchmark 10-year German bund yields, meanwhile, are on track for their biggest one-week decline in seven months, having fallen 9 basis points to 0.56% in early Friday trading.

Global oil markets are headed for a one-week decline after Thursday's report from the International Energy Agency which suggested that supply is likely to outpace demand this year as U.S. drillers pump record amounts of crude in response to OPEC-led production cuts.

Brent crude contracts for May delivery, the global benchmark, were 11 cents lower from last night's close at $65.19 per barrel while WTI contracts for April gained 15 cents per barrel to $61.34 thanks in part to a weakening U.S. dollar.

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