U.S. Treasury Secretary Jacob Lew warned on Friday that Greece's new government is running out time to reach an emergency financing agreement.

"We urge the authorities to quickly and fully commit to technical negotiations with their international partners," Mr. Lew said in remarks to the IMF's policy committee and before a meeting with Greek Finance Minister Yanis Varoufakis.

"Not reaching agreement would create immediate hardship for Greece and uncertainties for Europe and the global economy more broadly," Mr. Lew said.

Greece's European creditors and officials from International Monetary Fund have expressed growing frustration with Athens, worried the new left-wing government won't do what is required by its lenders to unlock bailout funds before it runs out of money.

"There is undoubtedly a need for the negotiations to gain notably further momentum in the coming days and weeks in order for us to conclude a review in a timely manner," said Poul Thomsen, head of the IMF's European department and one of the chief architects of Greece's bailouts.

Economists and European officials warn the standoff in bailout talks could result in a default on Greece's obligations, triggering an unintentional exit from the monetary union. Mr. Thomsen said a bailout deal needs to be reached before June, when Athens faces a series of large payments coming due.

Write to Ian Talley at ian.talley@wsj.com

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