Ads from more than 400 brands are due to vanish from Facebook on Wednesday (July 1).
The likes of Coca-Cola and Starbucks have joined a one-month boycott over hate speech on the site.
U.S. civil rights groups enlisted multinationals to pressure the tech giant in the wake of George Floyd's death.
Last-ditch talks between Facebook executives and advertisers on Tuesday (June 30) failed to stop the boycott going ahead.
Sources said Facebook offered no new details about how they would tackle hate speech, and instead pointed back to recent press releases.
That frustrated advertisers who don’t believe existing plans go far enough.
A spokeswoman for Facebook Chief Executive Mark Zuckerberg said Tuesday he had agreed to meet with the boycott organizers.
The social network also said it would submit to an audit of its hate speech controls.
Last week Zuckerberg said his company would be strict about taking down offending posts:
"There's no newsworthiness exemption to content that incites violence or suppresses voting. Even if a, if a politician or government official says it, if we determine that content may lead to violence or deprive people of their right to vote, we are going to take that content down no matter who says it."
U.S. groups including the Anti-Defamation League and Color of Change started the 'Stop Hate for Profit' campaign after Floyd's death.
The boycott is unlikely to have a big financial impact on Facebook. Last year it said its top 100 advertisers made up less than a fifth of total ad revenue.
But news of the boycott has battered Facebook shares, wiping billions off its market value.