Sessions's role in the investigation and his supervision of the Justice Department have been marked by controversy.
Sessions's decision to recuse himself from matters related to the 2016 election campaign has greatly angered Trump. Some conservative lawmakers have called for Sessions to resign, arguing he has not reined in what they call a reckless FBI investigation of the President.
At times, the Attorney-General has struggled to explain what was said in private meetings that are now of interest to investigators.
During his confirmation hearing in early 2017, Sessions was asked what he would do if he learned there had been contacts between Russians and the Trump campaign, and he answered: "I did not have communications with the Russians.''
After the Washington Post reported that he met at least twice with Kislyak in 2016, Sessions announced he was recusing himself from investigations involving the election, based on the advice of Justice Department ethics lawyers.
He has since maintained that he misunderstood the scope of the question at his confirmation hearing, and that his meetings with Kislyak were fleeting or strictly in his capacity as a US senator. In announcing his recusal, Sessions said: "I never had meetings with Russian operatives or Russian intermediaries about the Trump campaign."
That assertion is contradicted by the accounts Kislyak provided to his superiors in Moscow, according to current and former U.S. officials.
Kislyak reported to his bosses that he discussed campaign-related matters, including policy issues important to Moscow, with Sessions during the 2016 presidential race.
At the time, Sessions was a top foreign policy adviser to Trump the candidate. Kislyak's account of the conversations were intercepted by US spy agencies, who regularly monitor the communications of senior Russian officials in the US and Russia.
In December, Sessions pushed FBI Director Christopher Wray to remove and replace some of his top aides, particularly Deputy Director Andrew McCabe. Trump and others have argued those top aides, who served at the FBI under Comey, are biased against the President.