With Greece given five days to reach an agreement ahead of an emergency summit attended by all 28 EU member states, President Barack Obama has made his first personal intervention in the crisis in months.
Obama spoke to both Greek Prime Minister Alexis Tspiras and German Chancellor Angela Merkel before the leaders gathered in Brussels.
The US President told Merkel:
It is in everyone’s interest to reach a durable agreement that will allow Greece to resume reforms, return to growth, and achieve debt sustainability within the eurozone, a White House statement said.
Tsipras is hoping to get a commitment from other leaders to write off some portion of the country’s €320bn debt mountain.
Read more: Tsipras wants a "final exit" from the crisis
But, Merkel has dismissed debt reflief plans as “out of the question” despite pressure from Washington.
This comes as Donald Tusk, head of the European Council warned that “this is the most critical moment in the history of the European Union”.
He also said Greece leaving the Euro would have irreparable geopolitical implications for the continent "If someone has any illusion that it will not be so, they are naive."
The comments come after creditors were frustrated by new Greek finance minister Euclid Tsakalotos’ empty handed arrival at talks.
These are the most severe warnings that Greece could leave the euro, the first and only country to do so in 15 years since the euro was introduced.
If a deal is not made, Greece is set to default on a €4.2bn payment to the European Central Bank on the 20 July, putting it on the path towards leaving the euro.
Tsipras will have to submit a request on Wednesday for short-term funds and a new rescue package from creditors, which will then be discussed on Thursday before a final attempt to reach a compromise at the weekend.
Until now I avoided talking about deadlines, but tonight I have to say it loud and clear - the final deadline ends this week. All of us are responsible for the crisis, and all of us have a responsibility to resolve it, said Tusk.