Economic reforms in highly indebted Greece are coming along slowly, but the Greeks have made many sacrifices and people must be patient, the head of the European Commission's special task force to help rebuild the Greek economy said on Thursday.

Greece meets its private creditors on Thursday for a second day of bargaining on a crucial bond swap deal, with time running out for reaching a compromise needed to avoid an unruly default.

Speaking on German television, Horst Reichenbach stressed the need for a quick agreement and continued disbursement of bailout payments.

No one I speak with dares to imagine what would happen if the coming weeks do not lead to a good result, if the private banks' participation cannot be agreed and if the next tranche of aid is not paid out, he said on German broadcaster ARD.

With austerity programs hitting Greek household finances hard, public opposition to reform is not surprising, he said.

It's clear the Greeks have been forced to make enormous sacrifices, and in many areas, he said. So strikes and demonstrations are not so surprising.

On the other hand, the political class knows that it must negotiate, that it must perform, that it must convince creditors, and that something must change in Greece.

He also urged patience from the international community.

Things are moving ahead slowly. We should not expect any miracles. We must be more generous as far as time frames go when it comes to Greece's reforms, he said.

He said that part of the problem lay with Athens' struggles in implementing reforms but he praised the progress Greece had made so far during the euro zone debt crisis.

The Greeks are good at making plans but not so good at implementing them. Our job is to implement existing plans, to advance this capacity and strengthen it, he said.

Greece has got up from the floor and more structural funds have been mobilized, which is exceptionally important during the current credit crunch.

(Reporting by Brian Rohan)