* Greece U-turn threatens euro zone debt deal * Euro support seen at $1.3565 for now * 1-month implied vols on eur/dlr hit 1-month high * Fed in focus, G20 meeting also eyed By Anirban Nag LONDON, Nov 2 (Reuters) - The euro edged up on Wednesday, rebounding from a three-week low against the dollar as investors took a breather from a deep sell-off in the past two days, although it was vulnerable to the downside on jitters over Greece's referendum. The euro was up 0.45 percent at $1.3756 , pulling away from the three-week low of $1.3608 struck on Tuesday on a bout of short covering by real money investors and speculators. It rose to a session high of $1.3803 on trading platform EBS, with near term resistance around $1.3845--the 50 percent retracement of the euro's drop from its Aug 29 high of $1.4550 to a low of $1.3145 on Oct. 4. It failed to hold gains above $1.38 with weak manufacturing PMI data from Germany, France, Italy backing views that the euro zone is tipping towards a deep slowdown and compounding the euro's struggles. A move by the European Financial Syability Facility--euro zone rescue fund-- to delay a syndicated issue of 10-year bonds also weighed on the common currency. . "After yesterday's sell-off, some bounce was expected but we think there are a lot of hurdles for the euro to clear and given the risk events, we do not see it rallying much," said Adam Myers, senior currency strategist at Credit Agricole. "The Greek referendum has triggered a wave of risk aversion and flows in to the dollar." The euro had dropped to the day's low of $1.3637 after Greek Prime Minister George Papandreou said he would push ahead with a referendum on an EU bailout deal, defying demands from lawmakers of his own party that he quit for jeopardising Greek membership of the euro. The focus is now on the government's confidence vote on Friday. If Papandreou loses the vote, a new general election will be called and most likely there will be no referendum. But this is likely to spark renewed uncertainty and increase the chances of a disorderly default by Greece and risk of contagion. Papandreou will also face the leaders of France and Germany, who summoned him for crisis talks in Cannes, before a G20 summit of major world economies. The options market also indicated a fair amount of pessimism about the euro, with volatility hitting a one-month high on Wednesday, suggesting investors see more need to hedge against any negative events that may come out of Europe. Implied volatility on one-month euro/dollar options, a gauge of expectations regarding a currency's price action, jumped to as high as 16.35 percent according to Reuters data, from two-month lows of 12.75 percent last week. FED UP NEXT Indeed, Morgan Stanley said any euro rebound from the pre-G20 meeting between Greece, Germany and France is likely to be limited, providing a renewed selling opportunity. So they continued to favour euro rebounds into the $1.3845 area, targeting a move towards $1.3365 initially then the $1.3145 early October low and new cycle lows at $1.3100. The euro could earn some relief as market attention turns to the outcome of a meeting of the Federal Reserve's policy-setting FOMC ending on Wednesday, which may prepare markets for further policy easing. But most analysts were sceptical that the Fed could turn the tide on the euro, expecting risk sentiment to sour further. That should see both the dollar and the yen benefit from safe-haven inflows. "In view of the most recent political disruptions in the euro area, all things being equal, euro/dollar rallies are likely to be contained to the $1.39-$1.3930 range even if the Federal Reserve surprises with more easing today," said Stephen Gallo, head of market analytics at Schneider Foreign Exchange. The Fed will release its post-meeting statement at 1630 GMT, and Chairman Ben Bernanke will hold a media briefing at 1815 GMT. The dollar lost 0.4 percent to 78.01 yen . Japan sold a record of nearly $100 billion worth of yen on Monday, driving the greenback from a record low of around 75.31 yen to a high of 79.55 yen.

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