Greece is widely expected to miss a crucial payment to the International Monetary Fund (IMF) on Tuesday—hours before its bailout officially ends at midnight and the country is left with few, if any, financial lifelines.
Greek officials have already warned the country is unable to pay the 1.6 billion euros ($1.8 billion) due to the IMF by 6 p.m. ET, after reforms-for-aid talks with creditors broke down at the weekend.
The Greek government on Tuesday proposed a new, two-year bailout deal with the European Stability Mechanism. This would be to "fully cover its financing needs and the simultaneous restructuring of debt," according to a translated press release from the office of the Greek Prime Minister.
Jeroen Dijsselbloem, the president of the Eurogroup, subsequently tweeted on Tuesday that there would be a teleconference to discuss an "official request" from the Greek government "received this afternoon" at 1 p.m. ET.
This comes at a time when Greece's financial future is in jeopardy. The country will potentially have no access to external sources of cash, once its funding from the European Financial Stability Facility (EFSF) expires at midnight.
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Meanwhile, Greece's banking system is being kept afloat by emergency liquidity assistance (ELA) from the European Central Bank, which is up for review on Wednesday.
Against a backdrop of uncertainty, Tsipras has called a referendum on July 5 of the Greek people on whether to accept the bailout proposals—and accompanying austerity measures—proposed by creditors.
Tsipras has urged the public to vote "no" to more austerity.
"The Greek government will claim a sustainable agreement within the euro. This is the message of NO to a bad deal at the referendum on Sunday," the translated statement from the prime minister's office said on Tuesday.
Meanwhile, credit ratings agencies are increasingly nervous about the country's solvency.
Fitch Ratings downgraded Greek banks on Monday to "Restricted Default," after Athens imposed capital controls to prevent an exodus of deposits from Greece.
In addition, Standard & Poor's (S&P) lowered Greece's credit rating to CCC- from CCC, saying the probability of the country exiting the euro zone was now 50 percent.
Moritz Kraemer, chief rating officer of sovereign ratings at S&P, told CNBC on Tuesday that the group was "actually running out of notches" for Greece.
"We have the rating at CCC- and that's pretty much the lowest rung that we have on our scale," he told CNBC Europe's "Squawk Box."
If Greece misses its payment on Tuesday, then the IMF will consider it in "arrears" – a technical term used by the IMF, which is similar to default.
If a country is in arrears to the IMF, it means it won't get any future aid until the bill is repaid.
Although the IMF payment is dominating headlines, S&P's Kraemer said that Greece's bailout program ending at midnight was just as significant.
"Basically after that we're back to square one," he said. "So even if there was to be a change of heart in Athens and they did decide to take the creditors' offer, that's legally no longer possible as the program would have elapsed."
—With contribution from CNBC's Katy Barnato