(CNN) -- Attorney General Eric Holder said Tuesday the Justice Department blocked a proposed Texas voter identification law because it would "be harmful to minority voters."
In remarks prepared for a speech to an NAACP convention in Houston, Holder said getting a government-issued photo ID as the law requires would be difficult for many minority voters.
"Many of those without IDs would have to travel great distances to get them, and some would struggle to pay for the documents they might need to obtain them," he said.
According to Holder, recent studies show that 25% of voting age African-Americans in the United States do not possess a government-issued photo ID, while only 8% of voting age whites lack such identification.
The Justice Department blocked Texas' proposed ID law in March. The state is fighting that action in a hearing currently under way before a three-judge panel in the District of Columbia. Texas is required under the 1965 Voting Rights Act to secure federal approval of changes in its voting procedures.
In outlining his objections to the Texas law, Holder said he also objects because student IDs would not be accepted while concealed handgun licenses would be.
Supporters of the Texas law say it is needed to help prevent fraudulent voting.
"In our efforts to protect voting rights and to prevent voting fraud, we will be vigilant and strong," Holder said. "But let me be clear: We will not allow political pretexts to disenfranchise American citizens of their most precious right."
In objecting to the Texas law, the Justice Department said it reviewed the state's own statistics showing 600,000 registered voters lack a driver's license or another form of government identification.
The Washington hearing on the Texas law began Monday and the state official in charge of the elections division was among those to testify in support of the law. Keith Ingram cited Loving County in the western part of the state as an example of voter fraud. The count has a population of around 70 people, he said, but voter registration is 157% of that number.
Ingram also said that statewide, his office had identified at least 239 dead people listed as having voted in the past year. Under cross-examination he said clerical error may have accounted for such a high figure and that only four people had "definitely" been tied to voter fraud.
CNN's Bill Mears contributed to this report.