The latest round of talks between Greek and EU officials in Brussels has failed to reach an agreement.
A European Commission spokesman said while that progress was made on Sunday, "significant gaps" remained.
Europe wants Greece to make spending cuts worth €2bn (£1.44bn), to secure a deal that will unlock bailout funds.
Greek deputy prime minister Yannis Dragasakis said that Athens was still ready to negotiate with its lenders.
He said Greek government proposals submitted on Sunday had fully covered the fiscal deficit as demanded.
However, Mr Dragasakis added that the EU and IMF still wanted Greece to cut pensions - something Athens has said it would never accept.
IMF chief economist Olivier Blanchard said in a blog post that an agreement will require "difficult decisions", with "tough choices and tough commitments to be made on both sides".
The cash-strapped nation is trying to agree a funding deal with the European Union and IMF before the end of June to avoid a default.
Eurozone finance ministers will discuss Greece when they meet on Thursday. The gathering is regarded as Greece's last chance to strike a deal.
The Commission spokesman said: "President [Jean-Claude] Juncker remains convinced that with stronger reform efforts on the Greek side and political will on all sides, a solution can still be found before the end of the month."
The talks come as Germany ramps up pressure on Greece. Vice-chancellor Sigmar Gabriel said on Sunday that European nations were losing patience with Greece.
Germany wanted to keep Greece in the eurozone, but writing in Bild he warned that "not only is time running out, but so too is patience across Europe".
Mr Sigmar is also economy minister and head of junior coalition partners the Social Democrats.
His article is seen as a warning, particularly as his party has been more sympathetic to Greece in the past.
"Everywhere in Europe, the sentiment is growing that enough is enough," he wrote.
Greece is seeking to avoid defaulting on a €1.5bn debt repayment to the IMF due by the end of the month.
Creditors have demanded cuts in spending in return for another tranche of bailout funds.
But Greece's ruling left-wing Syriza party, led by Alexis Tsipras, was elected in January on promises to ease up on the highly unpopular austerity measures, increase the minimum monthly wage and create more jobs.
However, on Saturday Mr Tsipras warned the Greek people to prepare for a "difficult compromise".
My husband and I chose NCD to assist us in finding the perfect engagement ring that would compliment my style. We mostly dealt with Stephen who was very knowledgeable and really took the time to listen to what I was looking for and offered a really great selection of options to choose from. Thank you Stephen and NCD; I couldn't be any happier with my brand new canary yellow diamond ring. You wouldn't believe the compliments and interest that people give it. I just love it!! Thank you again for everything!
I have bought several coloured diamonds from Northern Cross Diamonds. I have found that Northern Cross gets me the best prices -- even when the diamonds come from another vendor and are listed with the other vendors at a higher price. Stephen Mitanidis has spent hours of his time educating me on coloured diamonds and helping me to choose diamonds that have the best investment potential. He has also allowed me to trade coloured diamonds that I own for coloured diamonds that I want and has assured me that Northern Cross will help me to sell my coloured diamonds if I choose to do so. If you buy a coloured diamond, I recommend that you consider showing it to your family members and friends. Most of them will be impressed with how it looks and might want to seize the opportunity to buy one or more before the value of coloured diamonds appreciates further.
I found Northern Cross Diamonds because I was looking for a colored diamond for an engagement ring to propose with. There are not many companies that have colored diamonds but they have quite a few. After considering for a couple of weeks, I decided to contact them to discuss the diamond I was looking at. The guy I worked with, Stephen, was very kind and helped me with the purchase process. I even had to ask them to ship my stone across the world to China. After I received it I had no doubt about the high quality of their products. I appreciate Stephen and Northern Cross to help me to achieve my perfect proposal plan. I am very happy to have done buisness with them and I will definately recommend Northern Cross Diamonds to anyone looking to get married or who would like to add more stones for their collection. Again, thank you Stephen
We accept Credit Card, Wire Transfer payments and provide Free, Fully Insured, Trackable Shipping to anywhere in the world.
All of our diamonds are Guaranteed Natural Coloured are GIA certified and 100% Conflict-Free.
Northern Cross Diamonds fully stands behind every single product that we sell. If you are unsatisfied with any portion of your transaction we will provide a 100% refund of our product within 30 days of purchase. No questions asked and no obligations. That is our promise to you.