GLOBAL MARKETS-Sharp decline in U.S. dollar lifts stocks, oil

* Euro has best week against the dollar since 2011

* Nasdaq close is highest in 15 years; S&P 500 up 2.7 pct for week

* Oil sharply higher despite oversupply concerns

* European stocks helped after Athens' assurances (Updates to the close of U.S. trading)

By Ryan Vlastelica

NEW YORK, March 20 (Reuters) - The U.S. dollar fell sharply on Friday and posted its biggest weekly decline against the euro in more than three years, helping to drive a rally in Wall Street stocks and crude oil.

The Nasdaq posted its highest close in 15 years on Friday and had a weekly gain of 3.2 percent.

Riskier assets like equities had a strong week in general, largely driven by the Federal Reserve's policy statement on Wednesday, which struck a more dovish tone than investors had expected. The Fed appeared to argue against an interest rate hike in June.

The U.S. dollar index is up more than 20 percent since mid-2014. The dollar's strength for some time buoyed U.S. stocks because it served as evidence of a strengthening economy, but lately there have been concerns of the impact it could have on the profits of U.S. multinational companies.

U.S. crude futures had their first weekly advance of the past five, and the S&P 500 snapped a three-week losing streak on Friday. The euro posted its biggest weekly jump against the dollar in more than three years, while the U.S. dollar index suffered its biggest weekly drop since 2011.

The dollar index, which measures the greenback against a basket of currencies, fell 1.37 percent, its biggest one-day decline since September 2013. The euro rose 1.4 percent, to $1.0811, and the yen rose 0.61 percent against the dollar.

"This is just some counter-trend correction in the dollar and is transitory," said Mark Luschini, chief investment strategist at Janney Montgomery Scott in Philadelphia.

Wall Street stocks surged, with the Dow and the S&P 500 both gaining almost 1 percent on Friday. For the week, the Dow rose 2.1 percent and the S&P rose 2.7 percent.

MSCI (NYSE: MSCI - news) 's all-country world index of equity performance in 46 countries rose 1.3 percent.

The Dow Jones industrial average rose 168.36 points, or 0.94 percent, to 18,127.39, the S&P 500 gained 18.82 points, or 0.9 percent, to 2,108.09 and the Nasdaq Composite added 34.04 points, or 0.68 percent, to 5,026.42.

"The Federal Reserve's created a situation where there's very little alternative to equities, so the path of least resistance for stocks will be up for a period of time," said Robert Lutts, president, chief investment officer at Cabot Money Management in Salem, Massachusetts.

Shares (Berlin: DI6.BE - news) of Nike Inc (Sao Paolo: NIKE34.SA - news) , the world's largest sportswear maker and a Dow component, jumped 3.7 percent to $101.98 a day after reporting strong quarterly results, though it warned about the impact of the dollar on the current quarter.

The Nasdaq Biotech Index rose 0.5 percent, powered by a 9.8 percent gain in Biogen Idec (NasdaqGS: BIIB - news) after the company announced promising results of an early-stage study of its drug to treat Alzheimer's.

European equities closed higher. The FTSEurofirst 300 index posted its highest close since mid-2007, finishing up 0.8 percent at 1,610.93. Greek equities rose 2.9 percent after Greek Prime Minister Alexis Tsipras assured European Union creditors his coalition would soon present economic reforms to unlock cash to stave off bankruptcy. In addition, the recent weakness of the euro was seen as boosting the region's economy and corporate earnings.

The benchmark 10-year U.S. Treasury note rose 15/32 in price, pushing the yield down to 1.9216 percent.

Brent crude rose 1.6 percent to settle at $55.32 per barrel while U.S. crude futures for April delivery jumped 4 percent to settle at $45.72. While concerns remain about oversupply, oil was boosted by the dollar's decline.

Both gold and silver rose for a third straight session, also helped by the dollar's weakness. Gold rose 1 percent while silver jumped 3.9 percent. Copper rose 3.3 percent. (Additional reporting by Gertrude Chavez-Dreyfuss and Chuck Mikolajczak; Editing by Leslie Adler)