Greece΄s Prime Minister Alexis Tsipras received a cool welcome Friday from the president of the European Commission, Jean-Claude Juncker, amid heightening tensions between Athens and other European capitals.

“I am not satisfied with the developments in recent weeks,” Mr. Juncker said as he received Mr. Tsipras at the commission΄s headquarters in Brussels. “I don΄t think we have made sufficient progress.”

Mr. Tsipras had requested a meeting with Mr. Juncker just as technical talks between Greece and the three institutions that have been overseeing its bailout-the commission, the European Central Bank and the International Monetary Fund–started in Brussels and Athens this week. Greece΄s left-wing government has been staking its hopes on the commission, the EU΄s executive, helping it to argue for more leeway on implementing economic overhauls and to get its hands on a much-needed slice of rescue money.

But Mr. Juncker warned against expecting too much from Friday΄s meeting. “The commission is not a major player in this,” he told journalists and Mr. Tsipras, adding that all decisions on Greece΄s bailout and the accompanying measures had to be taken by eurozone finance ministers.

Concerns about Greece΄s future in the eurozone have grown in recent weeks-despite a decision to extend the country΄s existing EUR240 billion bailout by four months until the end of June. Since that decision was taken in late February, progress on defining the overhauls the Greek government will implement in return for sustained help has stalled. At the same time, Mr. Tsipras and other members of his government haven΄t dialed back their antiausterity rhetoric and continue to ask for reparations from Germany for its actions in World War II-a demand that has alienated politicians in Germany and other eurozone countries.

Still, Mr. Juncker ruled out a Greek exit from the currency union. “I do not want a failure; this is not a time for division,” he said.

Earlier Friday, following a meeting with Martin Schulz, the president of the European Parliament, Mr. Tsipras said he was optimistic that tensions between Athens and the rest of the eurozone could be resolved. But some of his comments are unlikely to gain much sympathy with his negotiation partners. “There is no Greece problem; there is a European problem,” Mr. Tsipras said, adding that his country had already started to implement elements of its agreement with the rest of the eurozone.

“We are doing our part and we expect our partners to do their own,” he said.