US President George W Bush has signed into law a 25-year extension to the Voting Rights Act, one of the key pieces of civil rights legislation.
Mr Bush says he is willing to defend the law in the courts
The 1965 act gives federal authorities jurisdiction over voting practices in nine, mainly southern, states.
It was renewed for the fourth time by Congress, despite objections of some members from the states covered by it.
Speaking at a White House ceremony, Mr Bush said Congress had reaffirmed that all men were created equal.
"My administration will vigorously enforce the provisions of this law, and we will defend it in court," the president added.
Relatives of some of the key figures of the civil rights movement, including Rosa Parks and Martin Luther King, were present at the White House signing ceremony.
The law was originally drafted to curb abuses in states which had prevented minorities from voting in elections.
Critics from the affected states argue the act represents a continuing form of punishment for historical practices which have long since been corrected.
There were also some objections from legislators worried about the growing influence of Spanish - the act contains a provision allowing ballot papers to be printed in languages other than English.