However, the German leader stressed that Athens would also have to respect the common European rules on deficits.
The EU "is not going to leave Greece on its own" she told reporters after a pre-summit meeting with French President Nicolas Sarkozy, Greek Prime Minister Georges Papandreou, European Central Bank chief Jean-Claude Trichet, EU president Herman van Rompuy and EU Commission chief Jose Manuel Barroso.
"But rules are rules and the rules must also be respected," Merkel added, with regard to Greece's swollen public deficit, currently more than four times the limit laid down by Brussels and the highest in the eurozone.
"It's on this basis that we will adopt a decision," Merkel stressed.
Earlier on Thursday, a European diplomatic source said Paris and Berlin want to see "much higher demands than the European Commission" has announced for Greece.
The two eurozone big hitters want Greece to provide "guarantees that it will respect the objective of reducing its deficit by four percentage points this year," a French diplomatic source said.
Both capitals are concerned that Greece's economic woes could spread, the source said.