US President George W Bush has announced fresh sanctions against Sudan over the four-year 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 push for a new UN Security Council resolution to put more pressure on President Omar al-Bashir.
More than 200,000 people have died in the four-year conflict between rebels and pro-government militias in Darfur.
"For too long the people of Darfur have suffered at the hands of a government that is complicit in the bombing, murder and rape of innocent civilians," Mr Bush said.
"My administration has called these actions by their rightful name: genocide.
"We're targeting sanctions against individuals responsible for violence."
SANCTIONS ON SUDAN
30 Sudanese firms targeted
Mostly firms in oil business
Three individuals listed
Barred from US banking system
Barred from business with US
It is unclear how much extra leverage the new US sanctions will bring, says BBC diplomatic correspondent Jonathan Marcus.
Mr Bush wants Sudan to allow more UN peacekeepers into Darfur and to stop backing the Janjaweed militias.
Sudan denies supporting the armed groups and says the suffering in Darfur has been exaggerated for political reasons.
The Sudanese government criticised the new sanctions as "unfair and untimely" and urged the rest of the world to ignore them.
"I think it [the US] has revealed its intentions and that it does not want stability," Majdhoub al-Khalifa, an adviser to the Sudanese president, told al-Jazeera television.
US sanctions imposed in 1997 mean Sudanese companies cannot use US dollars, making international trade more difficult.
But the effects of these measures have been limited as China has become one of Sudan's major trading partners, supplying arms to Sudan and buying more than half of its oil. It has also spent millions of dollars investing in Sudan's oil infrastructure.
Even before Mr Bush spoke, China condemned the fresh US sanctions and said investing in Sudan was a better way to stop the violence.
US officials said 30 companies controlled by the Sudanese government, mostly in the oil business, are now barred from the US banking system or from doing business with US firms or individuals.
Another company suspected of shipping arms to Sudan has also been added to the sanctions list.
Also targeted are three individuals, including a rebel leader, who are suspected of involvement in the violence in Darfur.
The AP news agency says these are:
- Ahmad Muhammed Harun, state minister for humanitarian affairs, accused of war crimes in Darfur by the International Criminal Court
- Sudan's head of military intelligence and security, Awad Ibn Auf
- Rebel Justice and Equality Movement leader Khalil Ibrahim.
After Mr Bush's announcement, European Union foreign policy chief Javier Solana said the bloc was open to considering new sanctions against Sudan.
He said the matter would be discussed on Wednesday at a meeting of G8 foreign ministers in Berlin.
Having given new UN Secretary General Ban Ki-moon some space, President Bush's patience has now run out, our correspondent says.
China - which wields a veto on the UN Security Council - has not agreed to support the tougher UN resolution wanted by the US.
On Friday, the Security Council endorsed proposals to let a combined UN-African Union peacekeeping force protect civilians and use force to prevent violence.
The existing AU force has been unable to stop the conflict.