Joe Biden’s presidential campaign sent a letter to Twitter Wednesday, asking that the platform reject any political ads placed by Donald Trump’s reelection campaign that are found to be misleading or false.

Twitter did not respond to the campaign’s request, but said, in a statement to The Verge Thursday night, that the Trump ad Biden’s campaign focused on — which baselessly claims the former vice president coerced Ukraine into firing a prosecutor tied to his son Hunter — did not violate the platform’s rules.

“The ad you cited is not currently in violation of our policies,” a Twitter spokesperson says. “Additionally, we’ve received the letter and intend to respond.” The Biden campaign did not immediately respond to a request for comment regarding Twitter’s statement.

The move follows a week of letters and requests from Biden’s campaign asking news media outlets and social media platforms to stop hosting false or misleading political ads. In letters obtained by The Verge, the Biden campaign pleads with Facebook and Twitter to block these advertisements:

No company should allow itself to be a tool to mislead the public on any issue, let alone on one as important as the health of our democracy. It is one thing to allow President Trump the platform to spread falsehoods from his own account; it is quite another to profit from paid ads echoing the same lies. We ask that you make that distinction — between the personal account of a politician and paid advertising content — just as Twitter does in every other context.

Earlier this week, Facebook responded to a similar request from Biden’s team and flat-out rejected the idea of banning misleading ads.

“Our approach is grounded in Facebook’s fundamental belief in free expression, respect for the democratic process, and the belief that, in mature democracies with a free press, political speech is already arguably the most scrutinized speech there is,” Katie Harbath, Facebook’s public policy director for global elections, wrote in a response letter. “Thus, when a politician speaks or makes an ad, we do not send it to third party fact checkers.”