Hours before former acting Attorney General Sally Yates was due to testify before a Senate subcommittee investigating Russian interference in the 2016 presidential election, President Trump offered what amounted to a prebuttal of sorts on Twitter.

“Ask Sally Yates, under oath, if she knows how classified information got into the newspapers soon after she explained it to W.H. Council,” Trump tweeted Monday.

Yates — who was fired by Trump in January after refusing to comply with his controversial executive order on immigration — is expected to talk to the committee about what led to the ouster of Michael Flynn, Trump’s first national security adviser. Flynn resigned after media reports revealed that he had discussed U.S.-imposed sanctions on Russia during the transition, and had misled Trump and Vice President Mike Pence about those discussions.

According to the Associated Press, Yates “is likely to testify Monday that she warned White House counsel Don McGahn on Jan. 26 that Flynn’s contacts — and the discrepancies between what the White House said happened on the calls and what actually occurred — had left him in a compromised position.”

Yet Flynn’s resignation did not come until Feb. 13 — nearly three weeks after Yates’ warning and three days after the Washington Post disclosed the conversations, information that it attributed to nine anonymous current and former officials “who had access to reports from U.S. intelligence and law enforcement agencies that routinely monitor the communications of Russian diplomats.”

On CNN, Gen. Michael Hayden, former CIA and National Security Agency director, predicted that the administration probably “won’t be enthusiastic” about the details that emerge.

Yates’ testimony, Hayden said, will describe “the chaos in the Trump White House” and “feed that darker narrative” about the ties between the Trump campaign and Russia.

The White House, in turn, is expected to paint Yates as a “Democratic operative who was out to get Trump from the beginning,” according to Axios.

On Twitter, Trump tried to shift blame for vetting Flynn to the Obama administration, which granted the retired general top secret security clearance in 2012, when he was nominated to be the director of the Defense Intelligence Agency.

“General Flynn was given the highest security clearance by the Obama Administration,” Trump tweeted. “But the Fake News seldom likes talking about that.”

Last month, the House Oversight Committee revealed that Flynn failed to disclose 2015 payments from Russia’s state-owned news agency, Russia Today, when he was renewing his security clearance in January 2016.

In an interview with Fox News on April 28, Trump placed the blame squarely on the Obama administration for not properly vetting Flynn.

“When they say we didn’t vet, well Obama I guess didn’t vet, because he was approved at the highest level of security by the Obama administration,” Trump said. “So when he came into our administration, for a short period of time, he came in, he was already approved.”

President Obama fired Flynn in 2014.

And according to multiple reports, Obama himself warned Trump not to hire Flynn when then-President-elect Trump met with Obama at the White House on Nov. 10.