Pressure has mounted on Chancellor Angela Merkel's government over the September 4 bombing of two fuel trucks near Kunduz, northern Afghanistan, carried out on the orders of German NATO commander Georg Klein.
Members of the German parliament's defence commission agreed on the need for an investigation, but are yet to set out how it will be conducted. The centre-left Social Democrats and the Greens want public hearings, but Merkel's centre-right Christian Democrats want any testimonies to be given behind closed doors.
Merkel's spokesman Ulrich Wilhelm said Wednesday that the German leader will not appear before the commission. But Green defence commission representative Omid Nouripour insisted that he will call for the German chancellor to testify in person.
According to NATO, the death toll in the strike including civilians was up to 142.
German media alleged last week that the defence ministry hushed up reports of civilian casualties and also suggested commanders on the ground did not adhere to the agreed rules of engagement.
Former Defence Minister Franz Josef Jung resigned from his position as labour minister over the allegations. He served as defence minister at the time and had previously insisted "only Taliban terrorists" died in the attack.
Armed forces chief of staff General Wolfgang Schneiderhan and another senior defence ministry official also stepped down over the affair.
With some 4,400 troops, Germany is the third-largest contributor of foreign soldiers in Afghanistan after the United States and Britain.
German Foreign Minister Guido Westerwelle said Wednesday that a decision on whether to increase troop numbers would be made in late January.