The US President, George W Bush, has announced new sanctions against Sudan over the Darfur conflict.
Mr Bush said more Sudanese companies and individuals involved in the violence in Darfur would be barred from trading or banking with the US.
He also said he would press the United Nations Security Council to put more pressure on President Omar al-Bashir.
Speaking at the White House, Mr Bush accused the president of using military forces and government-aligned militias to attack rebels and civilians in Darfur and blocking peace-making efforts.
The stricter sanctions will bar another 31 companies, including oil exporters, from US trade and financial dealings, and take aim at two top Sudanese government officials – Ahmed Haroun and Awad Ibn Auf.
According to US officials, the goal of the sanctions is to force Sudan to allow the full deployment of a UN peacekeeping force, disarm the Janjaweed militias, and let humanitarian aid reach the region.
Earlier, Sudan's foreign ministry said that the expanded sanctions would not be justified or timely and would not affect plans for a hybrid peacekeeping force in the Darfur region.
China, one of Sudan's main allies, criticised the sanctions even before they were officially announced.
The humanitarian agency, Goal, welcomed the news that Mr Bush was to seek tougher UN sanctions over Sudan's handling of the conflict in Darfur.
However the charity said they would have little effect without the backing of a fully-mandated contingent of UN peacekeepers.
Fighting by government-backed militias and rebel groups in the Darfur region of western Sudan has killed more than 200,000 people and driven about two million from their homes.
