By Alastair Macdonald BRUSSELS (Reuters) - Euro zone finance ministers piled pressure on Greek voters and their government on Wednesday by warning that negotiations on a new bailout would depend on the result of Sunday's referendum on previous EU credit terms. "We will come back to your request for financial stability support from the ESM (European Stability Mechanism) only after and on the basis of the outcome of the referendum," Jeroen Dijsselbloem, who chairs the Eurogroup, wrote to leftist Greek Prime Minister Alexis Tsipras, who is calling for a No vote. Dijsselbloem's one-page letter, published by EU officials, was sent in response to a request from Tsipras for a new loan which was briefly discussed by the Eurogroup in a conference call on Wednesday evening.