Germany on Wednesday said talks on a final debt deal to keep Athens in the euro were still far from finished, and stressed that acceptance by all three international creditors was essential.

"Our impression is that we have a long way to go," finance ministry spokesman Martin Jaeger said.

After Greek Prime Minister Alexis Tsipras launched a veiled attack on the International Monetary Fund over its apparent "non-acceptance" of certain proposals, Jaeger said: "There can only be a solution in the end that is backed by the three (lender) institutions. That applies in particular for the IMF."