Susanna Dudiyeva, whose 12-year-old son Zaurbek was among 331 people, half of them children, killed after Chechen rebels seized their school in southern Russia, said late on Tuesday that her grief gave her the right to speak frankly to Putin.
She and the Beslan Mothers' Committee she leads will tell him in the Kremlin on 2 September, a year and a day from the start of the siege, that official incompetence that made the bloodshed worse is being covered up, she said.
"I will say that we think President Putin is to blame for what happened. As for what else I will say, well I am unpredictable and I can't tell the exact words I will use, but it will be serious," she said in the group's office, where black-clad women meet daily to discuss their plans.
"We have the right to speak out. Our right to speak out was forced on us. We got this right at the price of our children's lives," said Dudiyeva, slim and pale in her mourning outfit of black dress and headscarf.
For a year, Beslan residents have demanded a meeting with Putin to ask how the tense stand-off collapsed into a bloody gunfight and inferno on 3 September.
The meeting is unusual because Putin usually steers clear of potentially embarrassing public encounters with angry voters.
Ordinary Russians he does meet are almost always deferential.
Putin visited Beslan immediately after the bloodshed but arrived at night, stayed a few hours and spent most of the time in meetings with officials.
The mothers also want to complain about the incompetence they say allowed Chechen rebels to drive to their small town from Chechnya along Russia's most heavily guarded roads.
Shamil Basayev, the Chechen warlord who says he organised the raid, said late on Tuesday that security forces allowed his fighters to reach Beslan as part of an ambush planned by Russian intelligence that went wrong.
Officials rejected his version.
An opinion poll published on Wednesday by Levada-Centre, a polling organisation, said half of the Russians questioned share the Beslan mothers' view that officials mishandled the response.