* Dollar at more than 3-mo high; euro, Swiss franc fall
* Euro falls 2 cents vs dollar to $1.4330
* Second Greece downgrade stokes worry about euro zone
* More upbeat Fed economic view helps dollar
* Some say too early to call end of dollar downtrend (Updates prices, adds US data, adds comment)
By Steven C. Johnson
NEW YORK, Dec 17 (Reuters) - The dollar soared on Thursday, nearing a 3-1/2-month high against the euro, a day after the Federal Reserve highlighted improvement in the U.S. economy and stood by plans to shutter in February most emergency lending.
The euro, which fell below $1.44 for the first time since early September, struggled after Standard & Poor's became the second ratings agency to downgrade Greece in just over a week, stoking fears about the euro zone country's public finances.
Data showing U.S. jobless claims unexpectedly rose last week tempered dollar gains, but a regional U.S. factory index improved, leaving the greenback near a two-month high against sterling and up more than 1 percent on the Australian dollar.
The dollar's rise in thin, pre-holiday conditions triggered a wave of automatic buy orders, traders said.
"The U.S. economy is picking up, and the Fed acknowledged this by saying it will stop most of its quantitative easing by Feb. 1, while the Greece issue might create a bad cloud over the euro zone economy," said Hidetoshi Yanagihara, senior currency trader at Mizuho Corporate Bank in New York.
The Fed gave no indication in Wednesday's statement that it was set to raise interest rates from near zero, stressing that they would stay low for an extended period. But it highlighted improvements in the economy, which markets have seen reflected in a slower pace of job losses and improved retail sales data.
The euro fell around two U.S. cents to $1.4330, according to Reuters data, its lowest level since Sept. 8. It was last at $1.4343, down 1.3 percent on the day. It also fell 0.9 percent to 129.30 yen.
Greek assets took a lashing after Standard & Poor's cut Greece's rating by one notch to BBB-plus from A-minus late in European hours on Wednesday.
Sterling hit a two-month low beneath $1.61 and was last down 1.3 percent at $1.6128. The dollar also hit a more than three-month peak against a basket of currencies.
The dollar rose 0.4 percent to 90.15 yen, its third straight day of gains against the Japanese currency. Yanagihara said a recent push higher in U.S. bond yields reflected U.S. economic improvement while Japan faces deflation risks.
The Australian dollar, which has ridden three central bank interest rate hikes to multi-month highs of late, hit a 10-week low at $0.8853 and was last off 1.5 percent.
For most of 2009, the dollar has struggled on the view that the Fed would keep interest rates low longer than other central banks and that the U.S. economy would lag the global recovery.
But if growth and interest rate differentials start to move in the dollar's favor, it could continue higher in 2010.
"Like the proverbial hot knife through butter, the dollar is moving sharply and violently higher, most notably relative to the euro, and we are now more and more convinced that this is something more than a mere correction," said Dennis Gartman, independent investor and author of The Gartman Letter.
He said an excess of negative dollar sentiment that drove it some 15 percent lower against the euro since March was finally starting to turn around.
Alan Ruskin, chief international strategist at RBS Securities, said that is subject to change, though, unless the euro falls below its 200-day moving average around $1.4175.
Though the U.S. data is encouraging, he said "only a concerted break of this level would lead to a major reevaluation of the dollar's longer-term trend."
The dollar was unmoved by an MNSI report quoting China's deputy governor as saying dollar depreciation would continue and that it was getting harder for foreign governments to buy Treasuries as the U.S. current account deficit shrank.