Greek Prime Minister Alexis Tsipras on Friday urged thousands of supporters gathered in Athens to vote "No" in the weekend referendum to "live with dignity in Europe".
In his address to at least 25,000 people gathered in the capital's Syntagma square in front of parliament, he rejected EU leaders' warnings that a "No" result in Sunday's plebiscite could see Greece forced to leave the eurozone.
"On Sunday, we are not simply deciding to remain in Europe -- we are deciding to live with dignity in Europe," he said.
"I call on you to say 'No' to ultimatums and to turn the back on those who would terrorise you," he said. "No one can ignore this passion and optimism."
Tsipras called the referendum just last weekend and insists it only asks Greek voters whether they are willing to swallow tougher austerity measures in return for bail-out funds from its creditors, the International Monetary Fund, the European Commission and the European Central Bank.
Germany, France, Italy and European Commission chief Jean-Claude Juncker, however, have all said a 'No' vote would be a vote against Greece's place in the euro, and maybe even in the European Union.
Juncker on Friday said Greece's negotiating position would be "dramatically weakened" if a 'No' prevailed.
He added that even if the 'Yes' vote wins, there would still be "difficult" negotiations ahead.
Greece owes 323 billion euros ($358 billion), a crippling amount that is 180 percent of its annual output.
Tsipras hopes a 'No' vote will give him a mandate to demand the creditors write off 30 percent of the debt they hold and allow a 20-year grace period before it starts reimbursing the rest.