Greece's international creditors have signalled they were ready to compromise to avert a debt default even as Athens warned it might skip an IMF loan repayment due this week.

Prime Minister Alexis Tsipras visited Brussels to see senior European officials, where he is expected to hear the terms of the plan drawn up this week at a meeting of top leaders, including German Chancellor Angela Merkel.

With time running out, and looking to draw a line under months of acrimonious negotiations, the creditors have effectively come up with a take-it-or-leave-it offer.

However, Mr Tsipras has produced a plan of his own and said he intended to discuss this document in Brussels, calling on eurozone partners to show some "realism" and urging a deal that would let Greece escape from "economic asphyxiation".

German Finance Minister Wolfgang Schaeuble said an initial look at Greece's reform suggestions indicated that talks aimed at securing an aid-for-reforms deal will take time.

"I have no information that anything decisive has changed in terms of substance," he said at an event in Berlin.

Looking for a compromise, the creditors will suggest Greece should post a budget surplus before interest payments of one percent of gross domestic product this year and two per cent in 2016, against 3 per cent and 4.5 per cent under the terms of the current plan, sources familiar with the proposal said.

By contrast, the sources said the Greek government, elected in January pledging to end years of bitter austerity, had suggested a primary surplus of 0.8 per cent this year and 1.5 per cent next year.

Athens also offered to curb early retirements to save on pension payouts in line with previous proposals, but it was not clear if it had offered any new concessions demanded by lenders on labour and pension reform.

It was also not clear if the major creditors - eurozone governments, the International Monetary Fund and European Central Bank - had shown any flexibility in these areas.

Sounding more upbeat and conciliatory than Germany, France suggested that an agreement was within reach.

"We are a few days or hours away from a possible deal on Greece," French President Francois Hollande said.

"Asking too much of Greece could stifle growth. But asking too little would have consequences for the euro zone as a whole."