MIDEAST STOCKS-Background mixed for Gulf; S&P upgrade may support Egypt

Mixed messages from the oil market and concern that full-scale fighting in Yemen may soon resume could leave Gulf bourses trading sideways on Sunday, while Egypt may stabilise after Standard and Poor's revised its debt outlook to positive. In Yemen, a five-day humanitarian truce agreed last week is to end in the early hours of Monday, and no new agreements have so far been announced to extend it. The Yemen conflict is not a big factor for the markets but investors in the Middle East and especial