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* Euro losses extend, drops through $1.3900
* Ireland central focus in euro zone periphery worries
* Yen gains across board, dollar back below 81.00 yen
By Hideyuki Sano and Charlotte Cooper
TOKYO, Nov 9 (Reuters) - The euro's losses deepened on Tuesday as resurfacing concerns about peripheral euro zone debt kept it under pressure, and as some players closed long euro plays against the dollar ahead of year-end book-closing.
The euro fell to its lowest in over a week against the dollar, testing support at $1.3835 and with potential for a slide to more important support at its Oct. 20 low around $1.3700.
The dollar eased against the yen with Tokyo dealers saying one foreign bank had been selling dollars, triggering stops around 80.80 yen which pushed it down and wiped out some of its strength.
One trader said there was also talk of large accounts in Asia selling the euro over the past day. The European currency was on the back foot against the yen, shedding 0.7 percent after a drop of 0.8 percent on Monday.
The market became very short dollars ahead of last week's Federal Reserve decision on additional bond buying and part of the euro's falls stem from unwinding of dollar short positions, while the market is turning whippy as liquidity thins.
Gareth Berry, strategist at UBS in Singapore, said the market was seeing concern about Ireland as a chance to get in and sell the euro after its rally from $1.27 in September to a 10-month high of $1.4283 last week.
"It could quickly become a dollar positive story given positioning being the way it is," Berry said.
A trader at a European bank said some macro players and Commodity Trading Advisers, who are short-term players, are closing their short positions in dollar forwards and futures ahead of their book closing at the end of this month or next.
However, they were still sticking to dollar bearish views and were buying dollar puts at the same time to capitalise on any further drop.
G20 battle lines: http://r.reuters.com/jux34q
Basel III; rule reshaping: http://r.reuters.com/zys68p
Gold price performance: http://link.reuters.com/juz44q
Trade, currency tensions simmer pre-G20 [ID:nSGE6A801L]
Obama hits back after China slates Fed moves
[ID:nTOE69K01G]
Some say many players have not had an easy year and might close their books earlier than normal, meaning liquidity could thin out towards the end of the month and into early December.
The euro fell 0.4 percent to $1.3872
A more important support is its Oct. 20 low of 1.3695, where a break could signal that the currency has peaked near term.
Against the yen, the euro shed 0.7 percent to 112.16 yen
The euro also hit two-month lows versus the Aussie at A$1.3685
EU Economics Commissioner Olli Rehn, on a visit to Ireland, said he had not discussed any need for an EU bailout with the country, and that he believed market confidence would be restored once the country published its four-year plan to cut debt.
Ireland is expected to publish details of its plan later this month. [ID:nLDE6A72EE]
Worries about a political impasse in Dublin ahead of a key budget vote saw 10-year Irish bond yields
"A clear-cut solution (and therefore a reversal in spread widening) seems unlikely and as long as uncertainty prevails, spreads will remain under pressure," said RBC Capital Markets strategist Matthew Strauss.
"That is good news for USD bulls, but sombre news for risk bulls as an escalation of these concerns could easily spill over into broad-based risk aversion, adversely affecting commodity currencies such as AUD and CAD."
The dollar index <.DXY><=USD>, a measure of its performance against a basket of currencies, edged up 0.2 percent to 77.19.
The dollar was still down 0.3 percent on the day at 80.95 yen
"Unless we have new trading factors, it's hard to see the dollar/yen rising above that level," said Daisuke Karakama, market economist at Mizuho Corporate Bank.
The Australian dollar, which tends to suffer if risk appetite retreats, fell 0.2 percent against the dollar
But fellow high-yielder the New Zealand dollar plunged 0.8 percent to $0.7819
The market is also watching this week's meeting of G20 leaders in South Korea, pitched as a chance for them to prevent a currency row escalating into a rush to protectionism that could imperil the global recovery.
But there is little sign of consensus and the meeting has been overshadowed by disagreements over the Fed's quantitative easing policy. Anticipation of the Fed move helped depress the dollar and raised fears it may cause a destabilising flow of money into emerging economies.
Concerns that the Fed's aggressive easing could stoke more inflation than it wants also helped to push spot gold