Vice President Joe Biden marched with black civil rights leaders Sunday in Selma, Alabama to commemorate the "Bloody Sunday" beating of voting rights marchers 48 years ago.

State police assaulted the original marchers in 1965 over the protest urging Congress to pass the 1965 Voting Rights Act that struck down rules that barred African Americans from voting, and ended white majority rule in the US South.

The vice president said his consciousness was shaped by television footage of the beatings by state troopers.

"We saw in stark relief the rank hatred, discrimination and violence that still existed in large parts of the nation," he said at the event highlighting the area's importance during the US civil rights era.

The annual gathering took on added importance this year among groups concerned with protecting Americans' civil liberties.

On Wednesday, the US Supreme Court appeared ready to overturn, at least in part, the 1965 voting rights law that guards against racial discrimination in US states with a segregationist past.

At issue is the law's Section 5, which requires nine mainly southern states and local governments in seven other states to obtain Justice Department approval for any changes in their electoral codes.

The case follows January's re-election of the first black US president, Barack Obama, which critics call evidence that the law is unnecessary.