* Concerns grow over currency policies ahead of G20
* S&P 500 hits highest level since Nov 2007 before backing off
* Treasuries prices fall after tepid 10-year auction
By Leah Schnurr
NEW YORK, Feb 13 (Reuters) - The yen ended a volatile trading session little changed on Wednesday as concerns about currency wars and the fallout from mixed messages from the G7 put added focus on a G20 meeting in Moscow later in the week.
The currency gave up some of its sharp gains from the previous session. Comments from Russian Deputy Finance Minister Sergei Storchak weighed on the yen after he said the currency had definitely been over-valued and that "there are no signs" Japan's monetary authorities were intervening.
Currencies have been volatile after a Group of Seven statement earlier this week on exchange rates, designed to calm talk of a currency war, instead triggered fresh concerns.
The G7 on Tuesday reaffirmed its commitment to market-determined exchange rates and said fiscal and monetary policies must not be directed at devaluing currencies - comments which at first were seen as supporting the recent weakness in the yen.
However, an official from the group, which links the United States, Japan, Germany, Britain, France, Italy and Canada, later said the statement was meant to signal concern about the yen's excessive moves.
The Bank of England's chief said on Wednesday the statement should be taken at face value and anonymous officials should not try to reinterpret it.
The consensus among investors is that the G7 is not exactly thrilled with the weak yen trend, said Samarjit Shankar, director of market strategy at BNY Mellon in Boston.
"There's a lot more two-way risk in the yen right now, because of an increase in risk aversion," said Shankar.
Analysts were concerned about an apparent lack of consensus at the G7 level in tackling the risks of competitive currency devaluations as countries try to spur growth through expansionist domestic monetary policies.
"Investors overall are wary to push the yen much lower ahead of the G20 meeting and there is a bias for some give-back after the massive decline of the yen over the past few months," said Omer Esiner, chief market analyst at Commonwealth Foreign Exchange in Washington, D.C.
The euro last traded at $1.3447, down 0.04 percent on the day, and was at 125.65 yen, down 0.1 percent.
The confusion sown by the G7 statement has heightened the possibility that policymakers will use a G20 meeting in Moscow on Friday and Saturday to make further comments, either about the yen or the risk of wider currency devaluations.
The focus of the current concerns in the currency markets is Japan, where Prime Minister Shinzo Abe's government is pushing for aggressive policies by the Bank of Japan to beat deflation through monetary expansion.
Anticipation of the bolder measures has sent the yen down nearly 20 percent against the dollar since November, sparking comments from policymakers in the euro area about the impact on the common currency as the region struggles with a recession.
"To me the statement says as long as price action is smooth, (G7 officials) are not going to do anything. So I stand by my point that we are going to have more yen weakness in the medium-term," said Vasileios Gkionakis, head of global FX strategy at UniCredit in London.
World stock markets struggled to gain further traction after the S&P 500 hit its highest intraday level since November 2007.
European shares gained, but a measure of world markets was little changed and the Dow Jones industrial average fell back from the 14,000 level. After hitting a more-than-five-year high, the S&P 500 sputtered for most of the day before ending a tad higher.
The fact that there are not many sellers after a consistent string of gains is positive and shows the uptrend is intact, said King Lip, chief investment officer at Baker Avenue Asset Management in San Francisco.
"Last year we had double-digit returns in the first quarter. It's fairly possible we can move higher from here," he said.
U.S. equities started the year on a strong note, helped by growth in corporate earnings and an early January rally after the full brunt of the so-called "fiscal cliff" of automatic tax hikes and spending cuts was averted. A lack of recent catalysts has kept gains more limited and the market has slowly ground higher on low volume.
The Dow Jones industrial average ended down 35.79 points, or 0.26 percent, at 13,982.91. The Standard & Poor's 500 Index edged up 0.90 point, or 0.06 percent, at 1,520.33. The Nasdaq Composite Index added 10.38 points, or 0.33 percent, to 3,196.88.
MSCI's world equity index edged up 0.1 percent, while the FTSE Eurofirst 300 index of top European companies ended up 0.4 percent.
Treasuries prices fell after a tepid sale of 10-year debt. The benchmark 10-year U.S. Treasury note was down 12/32 in price to yield 2.021 percent.