Greece and its international creditors will begin talks on a new international bailout worth up to 86 billion euros ($NZD143.49 billion) for the crisis-hit country next week, a Greek government source says.

Technical teams from the European Union, European Central Bank and the International Monetary Fund would begin arriving over the weekend, but talks to finalise the bailout deal would only begin on Tuesday, the source said on Saturday.

The heads of missions would arrive a day or two later in Athens, the source said, adding that they should be on site by Thursday.

A European Commission spokesperson, however, could not confirm the plans, saying only that the representatives would fly out to Athens "in the coming days".

The two sides are under enormous pressure to hammer out the rescue deal before August 20, when Athens is scheduled to make a loan repayment of 3.2 billion euros to the ECB that it cannot currently afford.

The European Commission's Declan Costello, Rasmus Ruffer of the ECB, Delia Velculescu of the IMF and Nicola Giammarioli from the European Stability Mechanism will attend as mission chiefs for the organisations, according to the source.

A few hours earlier, the source had said the heads of missions would be in Athens this weekend.

"The delay... is due to technical reasons and not due to political or diplomatic reasons," added the source.

Greece's radical-left government struck a deal on July 13 with the creditors to introduce tough economic reforms in exchange for the bailout, which it hopes will prevent it from defaulting on its enormous debt and crashing out of the eurozone.

But there appears to have been a delay in getting the ball rolling on talks to finalise the package.

Negotiators from the creditors - who have bailed Greece out twice already since 2010 - have not set foot in Athens for more than a year as hostility has grown between the two sides.