Trump has come under increasing pressure over Russia's interference in the election and alleged contacts between his entourage and Moscow.
Sessions' own meetings with the envoy took place much earlier, in July and September, just as accusations of Russian interference in the election were mounting, according to the Washington Post.
Despite the swirling controversy, few hard facts are publicly available on what US investigators know and suspect about the contacts and about Russia's alleged operation to disrupt the election last year.