Oil prices edged up in early Asian trading on Tuesday following a sharp 5 percent drop in the previous session, as high global production and a weakening economic outlook, especially in Asia, prompted analysts to warn of further falls. Oil output by the Organization of the Petroleum Exporting Countries (OPEC) reached the highest monthly level in recent history in July, and production could rise further if Iran achieves a plan to raise output by 500,000 barrels per day (bpd) as soon as sanctions are lifted.