Traders trod water in Asia on Wednesday as they nervously await a string of major events that could hammer global markets or fuel a rally.

Thursday sees Britain voting in general election, the European Central Bank's policy meeting and -- in what could be the biggest market-mover -- sacked FBI boss James Comey's testimony on President Donald Trump's campaign links to Russia.

Adding to the sense of unease is a brewing crisis in the Middle East, where Saudi Arabia, the UAE and Egypt cut off ties and transport links to Qatar citing its support for extremism.

There are worries the spat could turn into a wider conflict that takes in Qatar ally Iran, with Trump wading into the row in a series of tweets signalling support for Riyadh on the issue.

After a recent rally, trading floors have quietened as dealers take a wait-and-see attitude, lifting safe-haven assets such as the yen and gold.

“There seems to be a little bit of nervousness in the market over Comey’s testimony,” Greg McKenna, chief market strategist at AxiTrader, said in a note.

"Whether it is geopolitics and the Middle East, worries about James Comey's testimony, the ECB, or UK election, traders backed off a little overnight.”

The yen held at the 90.50 range against the dollar, more than 1.5 percent stronger than last week, while gold was hovering around seven-month highs. The two are considered safe bets in times of uncertainty.

On equity markets Tokyo's Nikkei was down 0.3 percent by the break as the strong yen hurt exporters, while Seoul slipped 0.1 percent and Wellington lost 0.7 percent.

Sydney shed 0.1 percent following data showing Australia's economic growth slowed sharply in the first quarter and missed expectations.

However, Shanghai was up 0.7 percent, Hong Kong added 0.1 percent and Singapore put on 0.3 percent.

On currency markets the pound is holding up against the dollar ahead of the British vote.

Sterling has come under pressure in the past few weeks as Prime Minister Theresa May's ruling Conservatives have seen their once-commanding lead almost wiped out by the opposition Labour Party, raising worries about uncertainty just weeks ahead of Brexit negotiations.

The euro also remains in good health following a string of positive indicators out of the eurozone, led by Germany, and expectations the ECB will start to tighten monetary policy soon -- possibly Thursday.

 - Key figures around 0230 GMT - 

Tokyo - Nikkei 225: DOWN 0.3 percent at 19,916.85 (break) 

Hong Kong - Hang Seng: UP 0.1 percent at 26,026.25

Shanghai - Composite: UP 0.7 percent at 3,125.03

Pound/dollar: DOWN at $1.2903 from $1.2910 at 2130 GMT

Euro/dollar: DOWN at $1.1271 from $1.1278 

Dollar/yen: UP at 109.50 yen from 109.42 yen

Oil - West Texas Intermediate: DOWN 16 cents at $48.03 per barrel

Oil - Brent North Sea: DOWN 17 cents at $49.95

New York - Dow: DOWN 0.2 percent at 21,136.23 (close)

London - FTSE 100: FLAT at 7,524.95 (close)