A deal to aid vulnerable euro economies remains valid but will require the "full involvement" of EU member states, German foreign minister Guido Westerwelle said in an interview published on Wednesday.
Westerwelle was responding to doubts expressed by Finland, Netherlands and Slovakia over the agreement at a summit last week to use the European Union's ESM bailout fund to carry out bond purchases on the secondary market.
"What was agreed by the European Union remains valid," Westerwelle said, ahead of talks between the main proponent of the deal, Italian Prime Minister Mario Monti, and German Chancellor Angela Merkel in Rome later on Wednesday.
"Only by sticking together as Europeans will we manage to get out of the crisis," he added, as a key meeting of euro zone finance ministers expected to thrash out the details of the agreement looms next Monday.
The minister also reiterated Germany's opposition to a pooling euro zone countries' debt in the form of eurobonds.
"A mutualisation of debt in Europe would be a fundamental construction error, which would put the European idea at risk. That is why this is not an objective for Germany, even in the long term," he said.
"Too little solidarity puts Europe at risk, but too much solidarity puts it equally at risk," he added.