European Parliament President Martin Schulz has cast doubt over Greek government promises to reopen banks in the next few days, and warned that Greece faces "dramatic" times ahead if its government does not make meaningful proposals on how to deal with its debt mountain in the wake of a referendum that rejected austerity.

Schulz said European leaders should discuss emergency humanitarian aid to the country, where banks have been closed for more than a week in the run-up to the referendum.

"The promise of the Minister of Finance that the banks will open tomorrow (6 July) and that money will be available from tomorrow or Tuesday seems to me very difficult and dangerous. Therefore, because I believe that the Greek people will be during the week and in every day more difficult situation, I think we should tomorrow – and at latest on Tuesday before the eurozone summit – discuss about a humanitarian aid programme for Greece," he said.

"I hope that the Greek government will in the next few hours make a meaningful and constructive proposal allowing that it is meaningful and possible to renegotiate. If not, we are entering into a very difficult and even dramatic time," Schulz said.