U.S. Treasury Secretary Jack Lew told Greek Prime Minister Alexis Tsipras on Sunday that Athens and its creditors needed to continue working toward a resolution ahead of a Greek referendum on the creditors' demands for austerity.
A U.S. Treasury spokesperson said Lew told Tsipras in a phone call that it was important for Athens to show a commitment to reforms and for all parties to discuss possible debt relief for Greece.
After bailout talks between the Greek government and foreign lenders broke down over the weekend, the European Central Bank froze vital funding support to Greece's banks, leaving Athens to take steps to keep the banking system from collapsing.
Lew told Tsipras that Washington was monitoring the situation closely and he offered to stay in close touch in the coming days, the spokesperson said.
The statement said Lew noted "the importance of all parties continuing to work to reach a solution, including both a commitment to reforms and a discussion of potential debt relief for Greece, in the run up to the July 5th referendum."
Lew also stressed the need for Greece "to take necessary steps to maintain financial stability" ahead of the referendum, including working closely with international partners, the Treasury statement said.
In phone calls on Saturday, Lew urged top European finance ministers and the International Monetary Fund to keep working together toward a "sustainable solution" to reforms in Greece and its recovery within the euro zone.
President Barack Obama and German Chancellor Angela Merkel also spoke on Sunday and agreed it was "critically important" to find ways to keep Greece in the euro zone, the White House said earlier.
(Reporting by Tim Ahmann; Editing by Peter Cooney & Kim Coghill)