The US president followed the example of the UN Security Council on Tuesday and imposed sanctions on four Sudanese accused of abuses in the conflict.
Bush also issued an executive order freezing the assets of anyone deemed to have posed a threat to the peace process or stability in Darfur. The order also prohibited US companies or individuals from dealing with those implicated.
For the past three years militia, backed by the Sudanese government, are alleged to have murdered thousands people from tribes in the region, burning villages and forcing more than two million people into refugee camps in Darfur and neighbouring Chad.
The four men subject to sanctions include a leader of the Khartoum-backed Janjawid militia and a commander of the rebel Sudanese Liberation Army.
Bush said he was taking the action because the violence in Darfur threatened the national security and foreign policy of the US.
The move comes as peace talks in Abuja, Nigeria, mediated by the African Union have until Sunday to reach a deal.
But Unicef warned on Wednesday that people continued to die daily in Darfur as violence and lack of money hampered humanitarian help, and malnutrition was rising again while aid workers have been unable to reach the region.
It said another 200,000 people had fled their homes in the past three months alone to escape fighting between rebels, the army and militias.
As more Americans become aware of the situation, a coalition of 160 religious, human rights and political groups has organised a rally in Washington for Sunday to demand that Bush press for a stronger multinational force to end the dispute and protect the people of Darfur.
Speakers included Nobel Peace Prize winner and Holocaust survivor Elie Wiesel, Washington's Roman Catholic Archbishop Theodore McCarrick, and the actor George Clooney, who visited Darfur last week.