US Secretary of State Condoleezza Rice has said the government of Sudan has a "credibility problem" regarding Darfur.
Condoleezza Rice says Sudan must do more to end violence to women
She demanded "action not words" to stop the violence in Darfur, during a visit to a camp housing some of the 2m people displaced by the conflict there.
Ms Rice earlier met Sudan's President Omar al-Bashir and John Garang, the new vice-president and former rebel leader.
In talks marred by scuffles between US and Sudanese staff, she told Mr Bashir he must end the crisis in Darfur.
Ms Rice later flew to Israel, where she is due to hold talks on its planned withdrawal from the Gaza Strip.
In her meeting with Mr Bashir, Ms Rice stressed that the US would hold him to account if he failed to act, particularly in stopping violence to women.
Ms Rice told reporters: "I said to the Sudanese government that they had a credibility problem with the international community... I have said, 'actions not words'."
She said speaking to abused women and humanitarian workers at the Abu Shouk camp, which houses some 55,000 displaced people, had made plain the crisis facing Darfur.
The secretary of state suggested the US might consider lifting some sanctions against Sudan on humanitarian grounds.
Ms Rice earlier demanded and received an apology after US officials and journalists were manhandled by Sudanese security staff at Mr Bashir's residence in Khartoum.
Journalists and some US aides were initially prevented from entering the meeting room, while some of those who tried to ask questions about Darfur were forcibly removed.
Ms Rice had said she hoped stability could be restored in Sudan, following a peace accord in the separate conflict in the south and the creation of a new unity government.
The US has described the violence in Darfur as genocide.
At least 180,000 people have died and about two million people have been forced from their homes in the two-year conflict in Darfur, blamed mainly on the pro-government Janjaweed militias.
US aid official Andrew Natsios said a reported drop in violence in the region since January was chiefly because there were no villages left to burn down.
The United Nations estimates 2,000 Sudanese villages have been completely or partially destroyed.