* Dollar weakens to lows vs yen, Aussie, Swiss franc
* Traders look to U.S. yields for direction in thin market
* Euro zone debt woes could come back to haunt euro
By Hideyuki Sano
TOKYO, Dec 30 (Reuters) - The dollar weakened broadly on Thursday, hitting a seven-week low against the yen and a 28-year low against the Australian currency as traders took falls in U.S. bond yields as a cue to sell it.
U.S. Treasury prices recovered on Wednesday, pushing yields sharply lower, after a $29 billion auction of seven-year notes drew surprisingly strong demand a day after a weak five-year sale. [
]"Some market players may be building up positions for the next year. As the Federal Reserve is expected to keep printing dollars, the dollar looks set to cheapen next year," said Tsutomu Soma, manager of foreign securities at Okasan Securities.
As the euro, a natural alternative for the dollar, is smarting from concerns over debt financing of the currency bloc's peripheral countries, investors may be turning to other currencies such as the yen, the Aussie and the Swiss franc, he said.
While the relationship with bond yields and the value of a currency is not always straightforward, lower yields can make a currency less attractive for investors chasing better returns.
The dollar slipped as low as 81.28 yen <JPY=>, its lowest in seven weeks and edging closer to a 15-year low of 80.21 yen hit in November.
As thin trading due to the New Year's holiday tends to exaggerate currency moves, market players say there is a risk of the dollar falling near the November low or even to its postwar low of 79.75 yen marked in 1995.
Data on U.S. initial jobless claims later in the day and more importantly U.S. manufacturing data due on Monday could provide the impetus to push the dollar down, they said.
Keiji Matsumoto, a strategist at Nikko Cordial Securities, said a rise in the Chinese yuan after China's rate hike last Saturday is supporting Asian currencies, including the yen.
The yuan <CNY=CFXS> hit a record high against the dollar on Thursday after the Chinese central bank set the yuan mid-point <CNY=SAEC> versus the dollar at a record high.
"There will be speculation that China may engineer a higher yuan ahead of Chinese President Hu Jintao's state visit to the United States next month," Matsumoto said. Hu will visit Washington on Jan. 19. [
]TWO-YEAR YIELDS
Some analysts said the dollar is likely to rise against the yen eventually as its levels are too low in light of its historical correlation with the two-year U.S. Treasury yield.
The correlation has broken down this month as the dollar fell even as the two-year yield rose, but some market players say that relationship will return next month when the market becomes more liquid as many market players will come back from holidays.
Osamu Takashima, chief Japan FX strategist at Citibank, estimates that the current level of two-year U.S. yields <US2YT=RR>, around 0.65 percent, points to around 88 yen for dollar/yen if the historical correlation holds.
The current level is about 3.7 sigma away from that level, meaning the dollar is at a cheap level relative to yields that should happen only once in 19 years, Takashima said.
"There is no reason to think that correlation has broken down. It's quite reasonable to think that it will return," he said.
He added that Japanese life insurers may buy more foreign bonds without currency hedging.
Some of Japan's biggest life insurers have said they could consider buying more foreign bonds without hedging if the dollar is around 80 yen. [
]The euro extended gains to $1.3237 <EUR=>, rising above $1.3226, a 38.2 percent retracement of its fall from $1.35 to $1.3055 earlier this month.
The euro's stubborn refusal to break below its 200-day moving average, now at $1.3086, has frustrated bearish investors who think the euro-zone debt crisis could spread to Spain and Portugal in early 2011.
On the upside, it could target $1.3275-80, its high on Tuesday as well as a 50 percent retracement of the fall.
Still, traders say concerns over debt in some euro zone countries could crop up at any time after many investors and policymakers come back from Christmas holidays.
Already on Wednesday, Ireland's opposition Labour Party threatened to call a vote of no confidence in the deeply unpopular government if it has not set a date for an election by the end of January.
The Australian dollar hit a fresh 28-year high of $1.0198 <AUD=D4> against the U.S. dollar, though small option barriers at $1.02 prevented further gains in the Aussie.
Rising commodity prices have boosted the Aussie and helped investors shrug off fears that a recent Chinese interest rate hike would slow China's economy and thus dampen demand for Australian exports. London Metal Exchange copper hit a record high. [
]The Swiss franc, which has attracted funds escaping euro zone debt, hit a new high record against the dollar of 0.9418 franc. <CHF=> (Additional reporting by Chikako Mogi; Editing by Michael Watson)