* Euro helped by hopes of Greek debt deal, PMI data * Dollar hits 3-mth low vs yen, sparking intervention talk * Greece, Portugal worries still seen weighing on euro * Decent German, Portuguese bond sales; US data ahead By Jessica Mortimer LONDON, Feb 1 (Reuters) - Encouraging manufacturing data and hopes of a deal on Greek debt lifted the euro on Wednesday and the yen hit a three-month high versus the dollar, fuelling speculation Japan's authorities may intervene to curb its strength. Greek Finance Minister Evangelos Venizelos said talks with private creditors on a bond swap deal that is key to the country avoiding an unruly default were "one formal step away". The euro was also helped as a euro zone manufacturing activity survey was revised up, with German factories posting growth, and by decent demand at auctions of German and Portuguese debt. The euro was up 0.4 percent at $1.3128, off an earlier low of $1.3026 on EBS that took it close to psychological support at $1.30. Traders said it extended gains after pushing through stop loss orders at $1.3080 and $1.3125, though offers around $1.3150 may limit its rise. "We had the euro zone PMI just slightly better than expected and the UK PMI also stronger than expected and there's probably talk going around that a (debt swap) agreement is imminent out of Greece," said Audrey Childe-Freeman, EMEA head of currency strategy at JPMorgan Private Bank. "All of those factors have revived the euro after the disappointing performance yesterday but it's not an all-clear yet," she said, adding a Greek debt deal would be needed for the euro to push above $1.3250. Athens must still convince international lenders it can push through spending cuts and labour reform while concerns grow that Portugal may follow in Greece's footsteps and be forced to restructure its debt. Analysts said the euro may be vulnerable to further falls while it remains below technical resistance at $1.3244, the 38.2 percent retracement of its October-January decline. YEN INTERVENTION ALERT Traders were on alert for possible Japanese intervention to stem the rise in the yen as the dollar fell to its lowest in three months versus the Japanese currency, particularly as the euro was also weak, staying below the key 100 yen level. The dollar fell to 76.039 yen on the EBS trading platform, its lowest since Oct. 31 when it hit a post-World War Two record low of 75.311 yen and prompted massive yen-selling intervention by Japanese authorities. The euro was up 0.2 percent at 99.91 yen, having earlier dropped to 99.25. "We are approaching the lows seen before the last round of intervention so obviously there's a lot of tension. It's a very unpleasant situation for the Japanese authorities given that euro/yen is below 100 yen," said Niels Christensen, currency strategist at Nordea in Copenhagen. The dollar looked poised to lose ground for a fifth straight day against the yen, pressured by last week's pledge by the Federal Reserve to keep interest rates near zero until late 2014 which pushed yields on U.S. Treasuries down sharply. This has dented dollar/yen, which is particularly sensitive to changes in U.S. borrowing costs. Focus will now turn to U.S. ISM manufacturing data at 1500 GMT and key U.S. jobs data on Friday. If these come in on the weak side this could increase the chances of more quantitative easing and weigh further on the dollar, analysts said. The dollar index was down 0.3 percent at 79.059, while markets watched for any moves from the Swiss National Bank as the euro traded near the floor it set at 1.20 Swiss francs. The euro was at 1.2043 francs, just above 1.2025 hit on Tuesday, its lowest since the floor was set in September. China's Purchasing Managers' Index earlier showed the manufacturing sector expanded modestly, easing concerns about the global economy and helping lift the Australian dollar up 0.5 percent to $1.0664.