By Carla Mozee, MarketWatch , Hiroyuki KachiWeak oil prices are a boost to the U.S. economy: analyst

LONDON (MarketWatch) -- The Russian ruble dropped to a new all-time low against the U.S. dollar on Friday while other oil-related currencies also got crushed a day after the Organization of the Petroleum Exporting Countries did nothing to alleviate an oil glut.

Russia's currency (USDRUB) on Friday traded at 49.965 against the greenback, its weakest level ever. The dollar bought 48.795 rubles late Thursday.

The ruble's fresh descent came as the U.S. dollar enjoyed another round of broad gains against currencies from oil-producing countries including Norway and Canada. Oil futures plunged, with the January Nymex contract (CLF5) dropping more than 10% to end at $66.15 a barrel.

The dollar bought 7.0215 Norwegian krone (USDNOK) versus 6.939 krone late Thursday, marking its strongest level versus the Norwegian currency since March 2009. The krone's weakness came even as Norway's unemployment rate fell to 2.6% in November and retail sales grew 0.6% in October, noted Charalambos Pissouros, senior technical analyst at IronFX, on Friday. 3

"[Following OPEC's decision to maintain its current output, the ongoing fall in oil prices is likely to keep NOK under selling pressure and the Norges Bank will probably remain on hold for longer than it would have otherwise," wrote Pissouros.

The dollar rose 0.7% versus the Canadian dollar (USDCAD) to fetch C$1.1426

Meanwhile. the Bank of Russia on Friday said it's extending limits on currency swaps for the next two weeks in a move to discourage bets on a weaker ruble.

"When you combine the fundamentals that Russia is facing right now," in the form of Western sanctions and the further fall in oil prices, "it's going to limit how much [the central bank] can improve the value of the ruble," said Jameel Ahmad, chief market analyst at FXTM.

The euro (EURUSD) fell 0.1% versus the dollar to $1.2443, while the ICE dollar index (DXY) , a measure of the U.S. unit against a basket of six major rivals, rose 0.8% to 88.337.

As for Japan, the dollar strengthened against the yen, with lower oil prices among the factors accelerating the selling of the Japanese currency.

The dollar (USDJPY) was at Yen118.66, up from Yen117.74 late Thursday in New York.

A fall in Japan's two-year, government-bond yield into negative territory for the first time ever, provided another catalyst for the dollar's strength against the yen. Expectations for a widening gap between U.S. and Japanese interest rates has been one of the drivers of the yen's decline against the greenback.

"I think the negative yield on the two-year note can be cited as one reason behind the yen weakness," said Akito Fukunaga director of bond research at Barclays in Tokyo.

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