* U.S. stocks struggle to hold gains
* Gold, non-U.S. currencies in demand as caution persists
* 30-year U.S. Treasury yields fall (Updates to U.S. midday trading; changes byline, dateline; previous LONDON)
By Trevor Hunnicutt
NEW YORK, Dec 28 (Reuters) - Investors gravitated to safe-haven assets on Friday as worries about the world economy persisted, cutting short a two-day rebound in U.S. stocks.
U.S. stocks see-sawed, making it difficult for world equity indexes to end one of the most brutal December selloffs in memory on a high note.
"Markets will likely remain treacherous in the New Year," Marc Chandler at Bannockburn securities told clients.
After fluctuating most of the morning, at midday the Dow Jones Industrial Average .DJI rose 43.89 points, or 0.19 percent, to 23,182.71, the S&P 500 .SPX gained 6.85 points, or 0.28 percent, to 2,495.68 and the Nasdaq Composite .IXIC added 21.03 points, or 0.32 percent, to 6,600.53. .N
The pan-European FTSEurofirst 300 index .FTEU3 rose 1.85 percent .EU and MSCI's gauge of stocks across the globe .MIWD00000PUS gained 0.58 percent to bring the global benchmark to a weekly gain over 1 percent.
Markets have swung wildly in a week shortened by the Christmas holiday. But even a late Santa Claus rally will do little to salve the 8 percent declines for the MSCI index this month and a year that brought gains for very few categories of financial assets, from stocks to bonds and commodities.
The dollar index .DXY fell 0.1 percent, with the euro EUR= up 0.1 percent to $1.1441 and Japanese yen JPY= strengthening 0.57 percent versus the greenback at 110.39 per dollar. The greenback is down about 0.9 percent this month. FRX/
That has boosted gold, a traditional safe haven whose appeal this year was hit by a stronger dollar, which makes the metal more expensive to buyers with other currencies. The metal XAU= is perched at six-month highs of $1,279.18 an ounce. GOL/
The steady drum beat of disappointing economic data has continued to reinforce caution, with Japan's industrial output contracting in November and retail sales showing sharply. Europe, German annual inflation slowed sharply in December while in the United States, National Association of Realtors data showed contracts to buy previously owned homes fell unexpectedly in November, the latest sign of weakness in the U.S. housing market. Bailey, a strategist at brokerage Raymond James, said dollar weakness was good news for non-U.S. assets.
"My feeling is... if we get the transmission mechanism of a lower dollar, stocks outside the U.S. are set up for a good 2019," Bailey said. "Once people get their heads around the fact the U.S. is not going to have yet another double-digit return year in 2019, you can look elsewhere."
That would be a relief to world markets that largely underperformed the United States in 2018.
U.S. Treasuries did not see a huge flight-to-safety move. Bonds have been helped in recent weeks by risk aversion, but also face a glut of supply as the U.S. government finances its growing deficit.
Short and medium-term bonds were little changed on Friday. The 30-year Treasury bond US30YT=RR last fell 6/32 in price to yield 3.0383 percent, from 3.029 percent late on Thursday. US/
U.S. crude oil futures CLcv1 managed to lift a bit further off 2-year lows after a near-40 percent decline this quarter. The Energy Information Administration reported U.S. crude stocks USOILC=ECI fell modestly last week. EIA/S
Brent crude LCOc1 futures fell 3 cents to $52.13 a barrel, a 0.1 percent loss, by 12:28 p.m. EST (1728 GMT). U.S. West Texas Intermediate (WTI) crude CLc1 futures rose 54 cents to $45.15 a barrel, a 1.2 percent gain. O/R
In Italy, 10-year yields IT10YT=RR are set for their biggest monthly drop since July 2015. In the last auction of the year, investors were willing to buy 10-year government bonds at 2.70 percent, down from 3.24 percent last month. auction could be a sign Italy has turned a corner after months of consternation over fractious talks on its spending plans with the European Union.
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