A key person in the events that led to the firing of President Donald Trump's former national security advisor will testify publicly on Monday — and the president will certainly have his eye on it.

Former acting Attorney General Sally Yates will speak to the Senate Judiciary Committee on Monday afternoon in its hearing on alleged Russian interference in the 2016 election. She is almost certain to discuss former national security advisor Michael Flynn, whom Trump removed in February after it was revealed that he lied about the nature of his conversations with Sergey Kislyak, the Russian ambassador to the United States. Yates had warned the White House beforehand that Flynn, a retired Army lieutenant general, could be vulnerable to Russian blackmail after he made the incorrect statements.

The Trump administration has faced questions about why it hired Flynn to the key post, particularly after it came to light that the Pentagon is investigating Flynn over whether he got permission to accept payments from foreign governments, including a 2015 speaking engagement in Moscow.

Trump attempted to get ahead of the testimony in Monday morning tweets. He noted that Flynn's security clearance was renewed under the Obama administration, adding that "the Fake News seldom likes talking about that."

General Flynn was given the highest security clearance by the Obama Administration - but the Fake News seldom likes talking about that.

Trump is correct that Flynn's clearance was renewed under Obama, but Flynn was removed from his defense intelligence post by the Obama administration in 2014. Critics have asked why the Trump administration didn't catch possible problems with Flynn during its own vetting process.

Obama warned Trump against hiring Flynn shortly after November's presidential election, NBC News reported. White House spokesman Sean Spicer argued Monday that the Obama administration could have taken steps to suspend Flynn's security clearance if the administration was "really concerned."

Obama "made it known that he wasn't exactly a fan of General Flynn's," Spicer said.

In his tweets Monday, Trump also took the unusual step of suggesting a topic that he hopes senators will address with Yates in the hearing. He said she should be questioned about "how classified information got into the newspapers soon after she explained it to W.H. Council."

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

The "council" Trump refers to is the White House counsel's office, the legal team that Yates warned about Flynn being potentially vulnerable to blackmail.

Asked if Trump suggested that Yates had a role in releasing classified information, a claim that no evidence currently supports, Spicer said Trump's tweet "speaks for itself."

The hearing comes amid congressional probes into Russia's influence on the election and possible ties between the Trump campaign and Russia. The FBI is conducting a separate counterintelligence investigation.

Flynn was a Trump campaign advisor before he was made part of the administration. His conversations with the Russian ambassador took place after Trump's election but before his inauguration, a period during which the incumbent administration has traditionally handled foreign policy.

Trump repeatedly has denied that his campaign colluded with Russia, and has even cast doubt on whether the Kremlin tried to influence the election at all. Moscow claims it did not try to meddle, though the Kremlin is widely believed to have interfered in the elections of multiple Western nations, including Sunday's election in France.

Trump fired Yates in late January after she told Justice Department lawyers not to defend Trump's first executive order restricting travel from seven Muslim-majority countries. That came before current Attorney General Jeff Sessions was confirmed by the Senate.