He told the daily Hannoversche Allgemeine Zeitung that determining who bore what part of the blame for the deadly violence in the Caucasus last month would have a bearing on future relations with the West.
"The question of who bears guilt and responsibility are not the priority when people are suffering, have lost their possessions and are forced to flee," he said. "But I have also said that in a second phase, in which we will define our medium- and long-term relations with the conflicting parties, the issue of who bears what part of the responsibility for the escalation to the point of a military conflict will play a role."
Steinmeier, tipped as a possible challenger next year to Chancellor Angela Merkel, urged Russia and Georgia to support the work of an independent team of investigators with military expertise.
"I see no lack of institutions, for example in the framework of the UN or the OSCE," that could run the probe, he said. "But until now there has above all been an unwillingness on both sides to take part in such an investigation."
Steinmeier will join his 26 European Union counterparts in the French town of Avignon later Friday for a meeting aimed at highlighting their unity ahead of crucial EU-Russia talks next week on seeking a way out of the crisis.
Georgia and Russia have accused each other of starting the five-day conflict over the Moscow-backed breakaway region of South Ossetia and have traded accusations of ethnic cleansing. Russia has since withdrawn some forces but left others deep inside Georgian territory.
Moscow's recognition last week of South Ossetia and another breakaway region, Abkhazia, as independent states drew condemnation from Georgia and many Western countries.
EU heads of state and government announced Monday a freeze on talks with Russia on a new strategic partnership pact pending the withdrawal of its forces from Georgia to the positions held before the conflict erupted on August 7.