* Dollar headed for best 1-day rise in 3-1/2 months vs yen
* U.S. private sector jobs rise; services index up
* Rise in Treasury yields seen benefiting the dollar
* Portugal borrowing costs soar, Spain issuance on horizon (Updates prices, adds quotes, background, changes byline)
By Julie Haviv
NEW YORK, Jan 5 (Reuters) - The dollar leaped higher on Wednesday and could continue to outperform other major currencies after a slew of optimistic U.S. data indicated that the world's largest economy was on a steady path to recovery.
The greenback was on pace for its biggest one-day gain against the yen in more than three months and more than two weeks against the euro.
The ADP Employer Services report, which showed U.S. private employers added 297,000 jobs in December, further propelled an already rising dollar. The ADP number was the largest increase on record, with data going back to 2000, and far exceeded market expectations for a gain of 100,000.
It has so far been a banner week for the dollar as upbeat U.S. economic data and worries about the ability of certain euro zone countries to sell an abundance of debt worked in favor of the greenback.
"There is a large appetite for the dollar as it is being viewed as the growth currency of choice," said Andrew Wilkinson, senior market analyst at Interactive Brokers in Greenwich, Connecticut.
In early afternoon New York trading, the dollar index, which measures the greenback's value against six other major currencies, was up 0.93 percent at 80.180 <.DXY>. The dollar surged 1.4 percent against the yen to 83.21 yen <JPY=>.
The euro fell 1.1 percent to $1.3157 <EUR=EBS>, touching the barrier at $1.3125 with a reportedly $15-$20 million payout. Traders said the seller of the option, who is on the hook for the payout, has bought a substantial amount of euros to try to keep it above $1.3125.
Traders are now focused on taking out an exotic option barrier at $1.3125 in euro/dollar, a bet that the euro zone single currency will not fall below that level by 10 a.m. EST (1500 GMT) on Thursday. Consequently, there has been some buying of the euro in efforts to defend that number.
Wilkinson said he expects the euro to fall below $1.30 by the end of the month.
"While core European countries are showing solid growth, there is a lot of baggage attached to that growth and it has the potential to explode on sovereign debt woes," he said. "The rise in Treasury yields, meanwhile, should prove to be a tail wind for the dollar."
U.S. Treasuries' prices plunged. For details, see [
]Rising yields tend to support the dollar as they reflect stronger growth. They also enhance the attractiveness of some dollar-denominated assets to investors.
A separate report showing the U.S services sector expanded as well in December also lifted the dollar.
For a wrap-up of U.S. data click on [
]."If, in fact, employment is kicking in, then that would set the tone for self-sustained growth, underpin interest rates, and very much underpin the dollar," said Bob Sinche, global head of FX strategy at RBS Global Banking and Markets in Stamford, Connecticut.
Analysts said the private sector employment report bodes well for Friday's U.S. nonfarm payrolls number, which is expected to show gains of 175,000 overall jobs -- and 180,000 private-sector jobs -- last month. [
]Earlier this week U.S. factory orders, construction spending and a manufacturing index showed stronger readings as well.
As a result, Sinche said, RBS is "pretty constructive on the dollar this year." He expects the euro to fall into the low $1.20s against the dollar by mid-year, while dollar/yen could rise above 85.
"We're definitely back to a 'buy dollar' mentality and the market is looking to take out key support levels for the euro," said Dean Popplewell, chief currency strategist at OANDA in Toronto.
One of those support levels is the 200-day moving average just below $1.31, which has staunchly supported the euro over the last two weeks and its breach could signal further selling.
Portugal, another debt-laden euro zone country, has come under increasing pressure from international debt markets on concerns it may be forced to follow Greece and Ireland and seek a bailout. Demand for Portuguese Treasury bills was solid on Wednesday but yields continued to rise. [
]Market focus was shifting to Spanish debt issuance for 2011, the first tranche of which comes up for auction next week. (Additional reporting by Gertrude Chavez-Dreyfuss; Editing by Diane Craft)