WASHINGTON — President Obama used the 50th anniversary of the Voting Rights Act on Thursday to urge Congress to restore key elements of the law, arguing that court decisions and state statutes that discourage “certain kinds of folks” from voting are threatening to erode the fundamental promise of the civil rights-era bulwark.

A half-century after the measure outlawed practices that barred blacks or other minorities from voting, Mr. Obama said the nation had “conceptually” rejected discrimination in balloting, a mark of “huge progress.”

But, he said, “In practice, we’ve still got problems,” including laws requiring that voters show identification before casting ballots and limiting early voting, which Mr. Obama said may appear neutral, but actually “have a disproportional effect on certain kinds of folks voting.”

“On the ground, there are still too many ways in which people are discouraged from voting,” said the president, who was joined by 160 civil rights leaders, activists and state and local officials who gathered at the White House to celebrate the law 50 years to the day after President Lyndon B. Johnson signed it.