US STOCKS-Wall St ends up after Citi results, retail sales
* Citigroup is one of S&P's biggest gainers after results
* Biotech shares reverse early gains, weigh on Nasdaq
* U.S. March retail sales post biggest gain in 1-1/2 years
* Brent crude prices jump; energy stocks follow
* Dow up 0.9 pct; S&P 500 up 0.8 pct; Nasdaq up 0.6 pct (Updates to close)
By Ryan Vlastelica
NEW YORK, April 14 (Reuters) - U.S. stocks closed higher on Monday as Citigroup's earnings and strong retail sales gave investors reasons to buy equities despite a resurgence of geopolitical uncertainties.
Equities opened higher as strong results from Citigroup and bullish retail sales data lifted sentiment, though shares lost ground in the last hour of trading. Both the Nasdaq and the S&P 500 briefly turned negative, though they subsequently returned to positive territory.
Geopolitical concerns returned to the forefront after pro-Russian separatists ignored an ultimatum to leave occupied government buildings in eastern Ukraine as a threatened military offensive by government forces failed to materialize. Rebels in the town of Slaviansk issued a bold call for Russian President Vladimir Putin to help them. Continuación...