German Chancellor Angela Merkel has rebuffed a call by the International Monetary Fund to give cash-strapped Greece more time to clean up its state finances.

"We have agreed on a procedure that makes sense and to which we will adhere to," Merkel spokesman Steffen Seibert told a regular press briefing in Berlin on Friday.

"We are working on the implementation of the present on-going programme and within the time frame, that this programme provides for." Seibert said.

He went on to say that Germany was waiting for the group of experts representing Greece's international lenders to report on Athens' progress in introducing economic reforms. "That is what in the end counts for us," he said.

The comments from Merkel came after Germany's finance minister, Wolfgang Schaeuble, clashed with IMF head Christine Lagarde at the IMF annual meeting in Tokyo.

IMF call

Lagarde said Athens could require two more years to get its budget under control.

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The IMF chief warned that because of lack of growth, market pressures and austerity measures already taken, "a little bit more time" was necessary.

"Given the ... lack of growth, given the market pressure, given the efforts that have been undertaken, a bit more time is necessary," she said.

The German finance minister rejected such a request, stressing that Athens should adhere to the current programme.

"We shouldn't speculate" about such a demand until a report by Greece's creditors, the "troika" of the IMF, the European Commission and the European Central Bank is released, Schaeuble said in Tokyo.

Schaeuble said that a change in the conditions of Greece's aid payments would confuse markets and lead to a lack of trust in politics. Greece had lost a lot of time by holding two elections and should contribute to rebuilding trust, he added.