Attorney General Jeff Sessions acknowledged Tuesday he was aware that Russian officials had tried to reach out to members of the Trump campaign but said he didn’t lie or commit perjury by not disclosing those attempts in previous testimony to Congress.

During a five-hour grilling before the House Judiciary Committee, Mr. Sessions also batted back accusations that he succumbed to political pressure by asking federal prosecutors to review a past FBI investigation of Russia’s purchase of uranium rights and connections to then-Secretary of State Hillary Clinton.

Mr. Sessions told lawmakers he had forgotten attending a March 2016 Trump campaign meeting in which foreign policy adviser George Papadopoulos had said he could help arrange a meeting between the campaign and Russian President Vladimir Putin. Mr. Sessions said he “had no recollection” of the meeting until it hit the news as part of a guilty plea Papadopoulos entered last month.

The attorney general, who was a top national security adviser to the campaign, said he “pushed back” against Papadopoulos’ suggestion for a meeting, but he did not recall the reactions of others who attended the meeting — including Mr. Trump.

“After reading his account, and to the best of my recollection, I believe that I wanted to make clear to him that he was not authorized to represent the campaign with the Russian government or any other foreign government, for that matter,” Mr. Sessions said, later adding that he was concerned Papadopoulos would go around “pretending to represent the Trump campaign.”

Democrats said the attorney general keeps changing his story when it comes to Russian contacts with the campaign.

“You testified under oath before the Senate Judiciary Committee in January, you subsequently corrected that testimony in a March 6 written submission and have been forced repeatedly to come back to the Senate and now the House to clarify,” said Rep. Hakeem S. Jeffries, New York Democrat.

Mr. Jeffries noted that, as a senator, Mr. Sessions voted in favor of removing then-President Bill Clinton from office after he was impeached on perjury charges and spoke about prosecuting a police officer who had lied in a deposition but later corrected his testimony.

“Mr. Jeffries, nobody, not you or anyone else, should be prosecuted, not me, or accused of perjury for answering the questions the way I did in this hearing,” Mr. Sessions said. “I’ve always tried to answer the questions accurately.”

Mr. Sessions also defended his handling of a June 2016 trip that former Trump campaign foreign policy adviser Carter Page planned to take to Russia. Mr. Page has told Congress the trip was not related to the campaign and that he told Mr. Sessions about it in passing over dinner.

“No, I didn’t tell him not to go to Russia,” Mr. Sessions said Tuesday. “Am I supposed to stop him from taking a trip?”

Democrats pressed Mr. Sessions over the Justice Department’s announcement that prosecutors have been tasked with reviewing the department’s handling of matters involving Mrs. Clinton.

Rep. John Conyers Jr., Michigan Democrat, displayed a series of recent tweets from the president demanding an investigation into Russia’s 2010 purchase of uranium rights and donations to the Clinton Foundation while Mrs. Clinton led the State Department.

Republicans have questioned the deal, which was approved during the Obama administration and gave Russian companies control of about 20 percent of U.S. uranium deposits.

The deal was approved by the Committee on Foreign Investment in the U.S., which is made up of nine top government officials — including Mrs. Clinton at the time.

“I have not been improperly influenced and would not be improperly influenced,” Mr. Sessions said. “The president speaks his mind. He is bold and direct about what he says. We do our duty every day based on the facts.”

Mr. Sessions declined to say whether he is recused from investigations that involve Mrs. Clinton, saying it might reveal the existence of such a probe.

The attorney general previously recused himself from matters related to the 2016 presidential campaign. That left responsibility for those matters with Deputy Attorney General Rod Rosenstein, who appointed Special Counsel Robert Mueller to take over the investigation into Russian interference in the election.

Republicans wanted to know why Mr. Sessions hasn’t yet appointed a special counsel to probe the uranium deal and also to look into former FBI Director James B. Comey’s handling of the Clinton email investigation last year.

“What’s it going to take to get a special counsel?” Rep. Jim Jordan said, while trying to get Mr. Sessions to divulge information about how an anti-Trump dossier was used by the FBI or whether its author was paid by the U.S. government.

“It sure looks like the FBI was paying the author of that document, and it sure looks like a major political party was working with the federal government to turn an opposition research document into an intelligence document. To take that to the FISA court so that they can get a warrant to spy on Americans associated with President Trump’s campaign, that’s what it looks like,” said Mr. Jordan, Ohio Republican.

Mr. Sessions responded that his department had to study the facts and decide if they warranted a special counsel.

“I would say ‘looks like’ is not enough basis to appoint a special counsel,” Mr. Sessions responded.