Dylan Martinez/Reuters
President Obama and German chancellor Merkel.
The two spoke on the phone on Sunday as the situation in Greece has grown increasingly chaotic over the last 48 hours.
In a statement, the White House said, "The leaders affirmed that their respective economic teams are carefully monitoring the situation and will remain in close touch."
"The two leaders agreed that it was critically important to make every effort to return to a path that will allow Greece to resume reforms and growth within the euro zone."
On Sunday, news broke that Greek banks would be closed on Monday and remain closed until at least July 5, when Greece is scheduled to hold a referendum on the latest bailout proposal from its European creditors.
Greek prime minister announced the referendum in a surprise announcement on Friday night.
It now looks like Greece will miss a €1.6 billion payment to the IMF due on Tuesday and appears as close to a "Grexit" as it did during the eurozone crisis of a few years ago.
Additional reporting by Reuters.