Greece has submitted a proposal for an agreement with its creditors as Athens seeks a deal that will unlock desperately needed rescue money.
Prime Minister Alexis Tspiras said the ball was now in Europe's court to prevent the potential breakup of the European Union.
Without more rescue loans, Greece could default on its debts this month and potentially drop out of Europe's currency bloc.
"It is now clear that the decision for whether they want to adapt to realism and emerge from the crisis without the division of Europe, the decision belongs to the political leadership of Europe," he said.
Mr Tsipras gave no indication of what the proposal might include, other than to say it was realistic. It was submitted to the European Central Bank, International Monetary Fund and European Commission last night.
His comments come after the leaders of Germany, France, the IMF, ECB and European Commission held an emergency meeting about Greece in Berlin.
According to a German government statement, all present at that meeting pledged to work "with great intensity" to seek a solution.
Greece must repay a total of about 1.6 billion euro (£1.2 billion) to the IMF this month, with the first instalment due on Friday.
It is uncertain that the country can afford to pay the roughly 303 million euro (£218 million) due, increasing the sense of urgency for an agreement to be reached by then that will unlock the remaining 7.2 billion euro (£5.2 billion) of its bailout.
There have been suggestions Greece could seek to bundle all the money it owes the IMF this month into one payment on June 30, an option permitted under IMF rules but rarely used.
Taking that route could buy more time to secure a deal, although Athens has not indicated it is considering it.
"I am optimistic," Mr Tsipras said. "I believe the political leadership of Europe will view our proposals with respect."
At last night's talks in Berlin, the ECB's Mario Draghi and IMF head Christine Lagarde joined a previously scheduled meeting at the chancellery between German chancellor Angela Merkel, French president Francois Hollande and the EU's Commission president Jean-Claude Juncker.
A German government statement said the five pledged to work "with great intensity" to seek a solution and agreed to stay in close contact with each other and the Greek government.
The leaders "were in very close contact during the last days and will continue to be - with each other as well as, of course, with the Greek government".
Mr Tsipras' government, a coalition of his radical left Syriza party and a small nationalist party, was elected in January on promises of repealing the deeply resented austerity measures that accompanied the international bailout that has kept Greece afloat for the last five years.
For the last four months the government has been locked in tortuous negotiations with its creditors over what reforms Athens must take in order to receive the final instalment of its 240 billion euro (£173 billion) bailout.
Major sticking points have included labour reform and further curtailing pensions.
Mr Tsipras said Greece's latest proposals include some compromise.
"We have made concessions because a compromise requires concessions," he said. "We know these concessions will be difficult but we have submitted a realistic proposal for Greece's exit from the crisis.
"A realistic plan whose acceptance by the institutions, the creditors and our partners in Europe would mark the end of the scenarios of the division of Europe."
Europe's economics and financial affairs commissioner Pierre Moscovici said talks were "fruitful" though there was more work to be done.
"There is real progress in these talks and there is a better understanding between the Greek government and its creditors," he said on France Inter radio.
Mr Moscovici said progress had been made on reforms to value added tax and the establishment of an independent tax agency, as well as administration reform, non-performing loans and pensions.
He indicated that talks could continue past Friday. "In the few weeks that are coming up we have to find a solution," he said.
Speaking earlier, Deputy Prime Minister Yannis Dragasakis said Greece was "ready to respond to whatever is asked of it" to reach an agreement, but that Athens would not accept an ultimatum from its creditors.
EU spokeswoman Mina Andreeva said Greece and its creditors still need to do more work to reach a deal. "The main message is that we are not there yet," she said.
Speaking earlier in the day, labour minister Panos Skourletis said Athens had given as much ground as it could.
"I believe the Greek government has made the maximum level of concessions - there is no margin left. No margin," he said on Skai television.