Jan 13 (Reuters) - The euro extended gains against the dollar on Friday, helped by media reports saying that a Greek debt swap deal may be close, as well as stop-loss buying, traders said. The euro rose 0.4 percent to $1.2870, pulling away from a 16-month low near $1.2662 hit earlier in the week. A deal with private creditors to voluntarily write down at least half the value of their Greek sovereign bonds has a good chance of happening in the coming days, the chief executive of French bank Societe Generale told newspaper Les Echos. Banks have made an "exceptional" effort and the final losses may go above the initially agreed 50 percent, Frederic Oudea said in an interview published on Les Echos' website on Thursday. "(The talks) have a good chance of reaching their end in the coming days," he said, echoing similar comments by the chairman of rival bank BNP Paribas on Jan. 6. "It's possible that the final losses will be higher than 50 percent." Earlier on Thursday the head of a private-sector bondholder group said time was running short to clinch a deal on the voluntary debt exchange, while euro zone sources said Athens might force reluctant investors to accept losses. ** For the latest news on Europe's debt crisis, see

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