Petros Giannakouris, Associated Press
Greek Prime Minister, Alexis Tsipras, arrives at his office for an emergency meeting, in Athens, Monday, June 15, 2015. Tsipras held an meeting with the team of Greek bailout negotiators, and said the talks had stalled on demands by the creditors — the other eurozone states and the IMF — for a new round of pension cuts, which his government rejected.

ATHENS, Greece — Greek officials said Monday they were ready to return to bailout talks "at any moment" after a breakdown in negotiations pushed the country closer toward bankruptcy and jolted international markets.

Prime Minister Alexis Tsipras called an emergency meeting with his team of bailout negotiators as concerns spiked in financial markets that Greece might be unable to find a solution with creditors before it has debts to pay at the end of the month.

Without new loans, Greece faces a debt default on June 30, could have to put limits on money transfers and could eventually drop out of the euro.

The Stoxx 50 index of leading European shares was down 2 percent and Greek shares traded 4.5 percent lower. Greek borrowing costs rose, in a clear sign that investors are more worried about default, with the yield on two-year bonds up 2.7 percentage points at 28.5 percent.

While remaining low, bond yields also rose in Italy, Spain and Portugal as investors worried those countries might be most affected by turmoil in Greece.

European officials urged Greece to swiftly resume negotiations with international creditors, which include eurozone states and the International Monetary Fund.

"Greece must not wait ... there's not a moment to lose," French President Francois Hollande said.

European Central Bank chief Mario Draghi told EU lawmakers in Brussels that "the ball lies squarely in the camp" of the Greek government.

An official present at the emergency meeting in Athens said a deal was not reached over the weekend because creditors' representatives were not authorized to decide on a renewed set of Greek proposals.

"We are awaiting an invitation from the (creditor) institutions and at any moment we will respond with the continuation of negotiations," the official said, speaking only on condition of anonymity because the meeting was ongoing.

Officials had hoped that the outlines of a deal could be discussed at a meeting of the 19 eurozone finance ministers in Luxembourg on Thursday, but those expectations are fading.

The meeting had been billed as a decisive moment in the protracted talks as the Greek bailout program runs out at the end of the month and Athens needs to pay some 1.6 billion euros to the IMF or risk a default. The negotiations center on freeing up 7.2 billion euros ($8.1 billion) to make sure Athens can keep paying off loans.

The two sides are at odds over who's to blame for the impasse.

European Commission spokeswoman Annika Breidthardt insisted Greece had been refusing to budge on key issues while the country's fellow euro countries, the ECB and IMF had made "quite substantial" concessions.

"It is not a one-way street," Breidthardt told reporters.

Tsipras sees it very differently. Greece's creditors, he argues, need to display "realism."

Tsipras said the talks had stalled on demands by the creditors for a new round of pension cuts, which his government rejected.

"It is a gross misrepresentation of facts to say that the institutions have called for cuts in individual pensions," said Breidthardt. "Yes, the pension system is one of the most expensive parts of spending. It is also one of the most expensive pension systems in Europe. And therefore a reform of the pension system is part of the requirement."

Greek and EU officials also said that the two sides were still at odds over proposed sales tax hikes and how big a budget surplus the country should have when excluding debt interest payments.

"This is not an issue of ideological stubbornness. It's about democracy ... We will patiently wait for the institutions to display realism," Tsipras wrote in the daily newspaper, Efimerida ton Syntakton.

Greece has proposed a surprise hike in bailout taxes, agreed to demands for additional sales-tax revenue and higher corporate taxes for large profitable businesses.

Hollande said he was likely to have the opportunity to speak soon with both Tsipras and German Chancellor Angela Merkel.

Sylvie Corbet reported from Paris. Raf Casert in Brussels, Geir Moulson in Berlin and David McHugh in Frankfurt, Germany, contributed. Follow Gatopoulos at http://www.twitter.com/dgatopoulos and Corbet at http://twitter.com/SylvieCorbet