A special summit of the African Union insisted that sitting heads of state should be exempt from appearing before the Hague-based court, and the bloc warned it would support a no-show at the ICC by Kenyan President Uhuru Kenyatta if the demand was not answered.
"What the summit decided is that President Kenyatta should not appear until the request we have made is actually answered," Ethiopian Foreign Minister Tedros Adhanom Ghebreyesus told reporters.
Kenyatta and his deputy William Ruto have been charged with crimes against humanity for allegedly masterminding a vicious campaign of ethnic violence that left at least 1,100 dead and more than 600,000 homeless after disputed 2007 elections.
Now allies and elected this year on a platform of national reconciliation, they argue the case is violating Kenyan sovereignty and hampering their running of the country.
Kenyatta's trial is due to start in The Hague on November 12, and if he fails to turn up the ICC could issue an arrest warrant - which would expose Kenya to diplomatic isolation.
"It stopped being the home of justice the day it became the toy of declining imperial powers," the president told his fellow African heads of state, accusing the ICC of "bias and race-hunting".
The ICC, set up in 2002 as the world's first permanent court to try genocide and war crimes, has so far issued indictments linked to conflicts in eight nations, all of them in Africa, and diplomats with the 54-member AU said there was a sentiment that the court was turning a blind eye to crimes committed in other parts of the world.
"Africa is not a third-rate territory of second-class peoples. We are not a project, or experiment of outsiders," he added.
