* Euro hit as Europe banking concerns rekindled
* Dollar rises on flight to safety
* Yen rise as traders watch for intervention
* Swiss franc hits record versus euro (Adds quote, details, updates prices)
By Wanfeng Zhou
NEW YORK, Sept 7 (Reuters) - The U.S. dollar rose against most major currencies but fell to a 15-year trough versus the yen on Tuesday as renewed concern about the health of European banks sparked aversion to risk.
World stocks retreated and the euro weakened broadly after a Wall Street Journal report said that recent stress tests of European banks sector underestimated some lenders' holdings of potentially risky government debt.
The yen was also bolstered after comments by Bank of Japan Governor Masaaki Shirakawa increased speculation that Japan was not preparing to act to stem the yen's strength in the near term.
"Equity is the quickest reflection of overall market confidence, and I will say that market confidence remains low," said Firas Askari, head of FX trading at BMO Capital Markets in Toronto. "So you are seeing a renewed, somewhat flight to quality and the U.S. dollar is bid across the board."
In late New York trading, the euro EUR= slipped 1.4 percent to $1.2689. It had earlier hit a session low of $1.2682, according to electronic trading platform EBS, well off a three-week high of $1.2920 hit on EBS on Monday EUR=EBS.
Worries about the banking sector saw yield spreads between peripheral euro zone government bonds and their German counterparts -- considered the safest in the euro zone -- widen, with Portuguese and Irish spreads in focus.
Traders said the focus was turning to significant option expiries on Thursday, when an estimated 1 billion euros are set to roll off at $1.2600.
A spike in risk aversion boosted the Swiss franc, pushing the euro EURCHF= 1.6 percent lower to 1.2818 francs. The pair hit a record low of 1.2812 francs, according to Reuters data. The dollar CHF= was down 0.2 percent at 1.0100 francs.
US DOLLAR BELOW 84 YEN
Against the yen, the dollar hit a 15-year low of 83.52 yen, according to Reuters data JPY=, and last traded at 83.78 yen, down 0.5 percent. The euro fell 1.9 percent to 106.33 yen EURJPY=.
The Bank of Japan's Shirakawa said monetary authorities could not control forex rates, increasing speculation that Japan was not preparing to act to stem the yen's strength at the moment. [ID:nTOE68606B]
Shirakawa "has essentially ruled out intervention in the near term," CitiFXWire analysts said in a client note, adding that the statement helped to encourage yen bulls.
Shirakawa's comments followed the BOJ's decision to hold off from additional monetary policy easing. [ID:nTOE68602K] However, Japanese Finance Minister Yoshihiko Noda on Tuesday said the government would take firm action on currencies when needed, saying recent moves were clearly one-sided. [ID:nTKX006976]
Ashraf Laidi, chief market strategist at CMC Markets in London said expectations that incumbent Prime Minister Naoto Kan will stave off a leadership challenge by rival Ichiro Ozawa also helped lift the yen [ID:nTOE68606H].
"The latter has shown vocal support in favour of yen-supressing intervention," he said.
Short of active currency intervention, the yen could continue pushing toward its all-time high of 79.75 set in April 1995 should equities stay weak, analysts said, though they said the currency's upside momentum is weakening.
Data from the Commodity Futures Trading Commission last Friday showed net long yen positions fell to 49,904 from 51,069 contracts in the week ended Aug. 31. Total long yen positions also dropped.
Andrew Wilkinson, senior analyst at Interactive Brokers Group in Greenwich, Connecticut, noted higher implied volatilities for December yen put options relative to calls, suggesting investors are bidding more to buy puts -- which give the buyer the right, but not the obligation, to sell an asset.
"It would indicate to me that option investors are looking for more of a pullback in the yen than they are for a rally," Wilkinson said. (Additional reporting by Nick Olivari; Editing by Leslie Adler)