U.S. stocks are poised for more upward momentum even as uncertainty over oil prices and Greek debt negotiations keeps the market on tenterhooks, analysts say. Strong fourth-quarter U.S. company earnings and signs of an overall improving economy, alongside what appears to be the start of a bottoming in crude oil prices, have given equities support. After starting 2015 with its sharpest monthly drop in a year and a spike in volatility, the benchmark S&P 500 (.SPX) hit an intraday record on Friday while the Dow Jones Industrial Average (.DJI) reached its highest point so far this year.