* Euro falls after Moody's says may cut Spain rating
* Euro debt worries lift Swiss franc to record vs euro
* Dollar gains ground as Treasury yields rise
(Updates prices, adds detail)
By Jessica Mortimer
LONDON, Dec 15 (Reuters) - The euro fell against the dollar and hit a record low versus the Swiss franc on Wednesday after Moody's said it may downgrade Spain's debt rating, refocusing attention on contagion risks from the euro zone crisis.
The Swiss currency gained as worries about debt problems in some European countries encouraged investors to reduce exposure to riskier euro zone assets and seek safer alternatives.
Moody's put Spain's Aa1 ratings on review for a possible downgrade, citing concerns about its mounting debt and 2011 funding needs, though it did not believe Spain would need an EU bailout, as Greece and Ireland have.
Contributing to the euro's fall, the dollar firmed after upbeat economic data lifted U.S. bond yields, enhancing the appeal of U.S. assets.
Concerns lingered, however, that U.S. fiscal problems could worsen due to a proposed extension to tax cuts even if the move helps the economy. Traders said that for some investors this made the Swiss franc a more attractive safe-haven asset than the dollar.
"The U.S. story is still very important, and the extension of the Bush tax cuts has enhanced the Swiss franc's safe haven status," said Stephan Maier, currency strategist at Unicredit in Milan.
He said the Moody's statement had weighed on the euro, but that the euro was also weakening due to portfolio rebalancing and investors reducing risks ahead of the end of the year.
The euro was down 0.3 percent against the dollar at $1.3351, off an earlier low of $1.3285 where traders reported sovereign demand for the single currency.
The euro was down 0.2 percent at 1.2814 Swiss francs, having hit a record low of 1.2758 on trading platform EBS.
The Moody's report on Spain pushed Spanish bond yields higher.
The focus is likely to remain on debt problems in the euro zone periphery, with a Portuguese debt auction on Wednesday showing yields rising, while Ireland's parliament is due to vote on an 85 billion euro EU/IMF rescue package later in the day.
"There is an unwillingness among investors to hold riskier euro zone bonds over the year end so they are selling and going into Swiss francs," said Carl Hammer, currency strategist at SEB in Stockholm.
He added that financial markets had not priced in the risk of Spain needing financial aid, which left plenty of scope for further falls in euro/dollar in the first half of 2011.
U.S. YIELDS
The dollar gained 0.2 percent against a basket of major currencies to 79.530, moving away from a three-week low of 78.819 plumbed on Tuesday.
The 10-year U.S. Treasury yield hit a seven-month high just above 3.50 percent in Asian trade, helped by above-forecast U.S. retail sales data.
The Federal Reserve reaffirmed after a policy meeting on Tuesday its commitment to buy $600 billion in bonds as it attempts to boost the economy.
The dollar rose 0.2 percent to 83.82 yen while the higher-yielding Australian dollar fell 0.6 percent to $0.9928, hurt by risk aversion as stocks and commodity prices fell.
U.S. data on Wednesday includes November consumer prices and industrial output. (Additional reporting by Neal Armstrong; Editing by Hugh Lawson)