"I have recused myself in the matters that deal with the Trump [presidential election] campaign,” Sessions said during a press conference on Thursday at the US Justice Department.
"I feel I should not be involved in investigating a campaign I had a role in," Sessions said.
However, he insisted he never met with Russian officials to discuss the election campaign.
Pressure is mounting on Sessions to either recuse himself from a possible investigation of the Trump administration’s connections to Russia or resign as attorney general.
The Washington Post reported on Wednesday that Sessions, a major policy adviser to the Trump campaign, had failed to disclose meetings with the Russian ambassador during the president's election campaign.
Sessions told his congressional confirmation hearing at the Senate Judiciary Committee on January 10 that he did not know of contacts between Trump campaign members and Russia.
The previously undisclosed meeting fed growing calls for Sessions to recuse himself from oversight of Justice Department and FBI probes into the alleged Russian meddling and contacts with Trump campaign advisers.
Democratic lawmakers had been urging for weeks for Sessions to step away from the investigation, though he had resisted pressures to do so. On Thursday, some senior Republican lawmakers joined in saying the former senator should recuse himself.
Trump said Thursday that he has "total" confidence in Sessions. Speaking aboard the aircraft carrier USS Gerald Ford in Newport News, Virginia, Trump told reporters that he was not aware of Sessions’s contact with the Russian ambassador.
Trump also said that Sessions "probably” testified truthfully during his confirmation hearing. Asked whether Sessions should recuse himself, Trump added: "I don’t think so.”
Sessions, 70, was confirmed by the Senate on February 8 to lead the powerful US Justice Department.
An early supporter of Trump, the former senator became America’s top law enforcement official after two decades of representing the state of Alabama in Congress.