* U.S. stocks gain in choppy trade, rising dollar weighs
* Euro breaks below $1.43 for first time since September
* Oil rises above $73 a barrel on news of Iran-Iraq row
* Bonds fall on profit-taking after Thursday's rally (Updates with U.S. markets close)
By Herbert Lash
NEW YORK, Dec 18 (Reuters) - The U.S. dollar gained broadly on Friday on improved economic sentiment and a safe-haven bid after Iranian soldiers crossed into Iraq and took up positions in a disputed southern oilfield, which also lifted oil prices.
The euro fell below $1.43 for the first time since early September, flushing out short dollar trades, while the dollar rose for a fourth consecutive day against the Japanese yen. For details, see [ID:nN18235960]
The dollar's advance led investors to pare risky bets earlier in the session, but U.S. stocks ended higher and trimmed the U.S. currency's gains.
Oil rose above $73 a barrel after Iran's incursion into an Iraqi oilfield sparked tension between two major crude exporters. [ID:nSGE5BH07L]
A cold snap in the U.S. Northeast, the biggest heating oil market in the world, also helped support prices.
Dollar strength forced investors who had bet on further weakness in the greenback to cover their short positions by selling equities or other assets.
"A strengthening dollar ... means, in my opinion, a rotation into quality," said Haag Sherman, co-founder and chief investment officer for Salient Partners, a Houston-based investment firm with $8 billion in client assets.
Trading was choppy as Friday marked the expiration of December options and futures.
The Dow Jones industrial average <.DJI> closed up 20.63 points, or 0.20 percent, at 10,328.89. The Standard & Poor's 500 Index <.SPX> was up 6.31 points, or 0.58 percent, at 1,102.39. The Nasdaq Composite Index <.IXIC> was up 31.64 points, or 1.45 percent, at 2,211.69.
The Nasdaq rose on upbeat results from Oracle
Oracle shares rose 6.4 percent, while RIM's Nasdaq-traded shares jumped 10.3 percent.
The dollar was up against a basket of major currencies, with the U.S. Dollar Index <.DXY> up 0.06 percent at 77.741.
The euro
"I think we're seeing a continued flight to safety," said Tom Schrader, managing director of U.S. equity trading at Stifel Nicolaus Capital Markets in Baltimore.
"The stronger the dollar gets it means investors will be unwinding the dollar carry trade and that's going to put upward pressure on the dollar and downward pressure on the stocks."
U.S. Treasury debt prices fell as profit-taking emerged after a safe-haven rally in bond markets on Thursday that was ignited by falling stocks and concerns about Greece's fiscal problems. [ID:nN18229631]
The benchmark 10-year U.S. Treasury note
At the end of the year investors are trying to position themselves for 2010, said Jerry Webman, chief economist at Oppenheimer Funds in New York.
"Everybody is trying to ask if there really is some of sort of synchronized global recovery, the answer to which I think is 'yes,' Webman said.
U.S. crude for January delivery
London Brent crude
Signs of improvement in the U.S. economy have helped the dollar in recent days, as did the Federal Reserve's pledge this week to wind down most stimulus measures by February, lifting hopes of a more robust U.S. recovery in 2010.
The dollar and Swiss franc also attracted safe-haven flows due to Iran-Iraq tensions.
Traders said all these factors encouraged a bout of position squaring, with investors buying back the dollar and taking profits on trades that had helped push the U.S. currency down more than 15 percent between March and November <.DXY>.
"There's a winding down of activity into year end, with people taking profits on core trades," said Samarjit Shankar, managing director of global FX strategy at BNY Mellon in Boston. "But the dollar has been well-supported lately, and given the positive surprises in U.S. data lately, people are looking at the U.S. recovery story now as a glass half full."
Spot gold prices
European shares closed lower, with banks falling as ongoing concerns about tough new Basel regulations weighed. The FTSEurofirst 300 <.FTEU3> index of leading European shares closed 0.5 percent lower at 1,013.15.
The MSCI index of Asia Pacific stocks traded outside Japan <.MIAPJ0000PUS>, which has rallied more than 60 percent this year, was 0.5 percent lower. In Japan, the Nikkei share index <.N225> dipped 0.2 percent, paring most of the day's losses. (Reporting by Ellis Mnyandu, Joshua Schneyer, Steven S. Johnson and Richard Leong in New York; Joe Brock and Joanne Frearson in London; writing by Herbert Lash; Editing by Kenneth Barry)