Greek Prime Minister Alexis Tsipras vowed to present "credible" reform plans before a Thursday deadline set by exasperated European leaders, as Athens formally asked for a new bailout to avoid crashing out of the euro.
Despite mounting fears of a looming "Grexit" from the single currency, the French and Spanish premiers on Wednesday welcomed the latest "positive" developments, just days before a deal needs to be reached for Athens to avoid bankruptcy.
Leftist leader Tsipras was greeted by a mixture of boos and cheers as he addressed the European Parliament, defending his decision to hold a bailout referendum last Sunday that dismayed Europe.
"The Greek government will tomorrow file new concrete proposals, credible reforms, for a fair and viable solution," Tsipras told European lawmakers in Strasbourg, France during a heated debate.
Tsipras also appealed for unity on all sides after six months of deep rifts with eurozone colleagues over the Greek debt crisis, saying: "Let us not allow it to become a divided Europe."
The Greek government promised it would start pension and tax reforms next week, as demanded by creditors, in return for a three-year loan to drag its financial system back from the brink of collapse.
French Prime Minister Manuel Valls said fresh proposals made by Athens in exchange for a new European bailout were a step in the right direction, describing the request as "balanced, positive".
He reiterated France's stance that keeping Greece in the eurozone was a "geopolitical issue of the highest importance".
Spanish Prime Minister Mariano Rajoy also said of Greece: "The tune has changed, it's not what we were hearing until now and that's positive."
EU President Donald Tusk however warned that a special summit of EU leaders on Sunday was the final chance for a deal to avoid a "Grexit", which would have global repercussions.
"This is really and truly the final wake-up call for Greece and for us, our last chance," said Tusk, warning that failure "may lead to the bankruptcy of Greece" and cause geopolitical problems for Europe.
Greece's banks remain closed for a second week, amid a cash crisis which saw the country last month become the first developed economy to default on an International Monetary Fund loan payment.
- 'Final deadline' -
Eurozone leaders lost patience at a crisis meeting in Brussels on Tuesday after Tsipras and his new Finance Minister Euclid Tsakalotos turned up without any concrete plans on paper.
They ordered Athens to file a complete reform plan by midnight (2200 GMT) on Thursday, with Tusk saying the "final deadline" for a deal would then be Sunday's summit of all 28 European Union leaders.
In a formal letter on Wednesday to the European Stability Mechanism, the lender of last resort set up during the eurozone debt crisis, Tsakalotos said Greece would "immediately implement a set of measures as early as the beginning of next week".
The ESM confirmed that it had "received the Greek request", the first step demanded by the eurozone leaders towards reaching a deal that many countries remain sceptical about.
Greece has had two previous international bailouts worth 240 billion euros, the last of which expired on June 30.
The price of those loans was five years of harsh austerity measures, and in Sunday's Greek referendum voters overwhelmingly rejected more of the same offered by international creditors.
But the cost of the 'No' vote is also draining Greece dry, with ATM withdrawals limited to just 60 euros per day for Greek bank card holders.
- Food, tourism fears -
Fears about food supplies in the next two or three weeks have mounted, businesses are unable to pay abroad for goods, and last-minute tourist reservations have plunged 30 percent, the Greek Tourism Confederation said.
The urgency of the situation was underlined by the head of France's central bank, Christian Noyer, who told French radio he feared Greece could descend into "chaos" unless a deal was struck this week.
A day after US President Barack Obama spoke to both Tsipras and Merkel by telephone about the crisis, US Treasury Secretary Jacob Lew said that Greece's creditors needed to give the country a path for debt restructure and growth.
"Greece's debt is not sustainable," he warned.
The European Central Bank has been providing emergency liquidity to keep Greek banks from collapsing, and on Wednesday decided to leave the limit on its stop-gap credit facility to Greece unchanged at 89 billion euros ($99 billion), a banking source said.
But further support will depend on political developments in Brussels and Athens.
World stocks were mixed, with Asian and US shares sinking but European stocks edging higher on hopes of a deal. The euro advanced to $1.1041 from a five-week low of $1.0916 in New York trade on Tuesday.