WASHINGTON — Sudan could be removed from the US list of state sponsors of terrorism as early as July if Khartoum recognizes the results of the referendum on independence for the south, a US official said Tuesday.

"Should the referendum be carried out successfully and the results are recognized by the government, President Obama would indicate his intention to begin the process of removing them," Princeton Lyman, the lead US negotiator with Sudan, told AFP.

"It is a process that takes some time, but by beginning the process in the wake of the referendum, the hope is if they meet all the conditions it can be done by July," Lyman said.

The referendum is widely expected to lead to mainly Christian and animist southern Sudan seceding from the predominantly Muslim north of the country.

Results are expected around the end of the month, US officials said.

Another key condition for removing Khartoum from the US blacklist is that it not "directly or indirectly" support terror groups, said Assistant Secretary of State for African Affairs, Johnnie Carson.

Countries on the list of state sponsors of terrorism cannot receive US aid or buy US weapons, and bilateral trade is restricted. The list currently includes Cuba, Iran, Sudan and Syria.

The United States has banned virtually all trade with Sudan since 1997.

But even if Khartoum is removed from the list, Washington would still expect Sudanese President Omar al-Bashir to answer charges of war crimes, crimes against humanity and genocide in Darfur, which have been leveled against him by the United Nations' International Criminal Court (ICC).

"The United States continues to believe that President Bashir should cooperate with the ICC," Carson said.

"The United States has taken a very clear position that you need to have justice and accountability with regard to Darfur and that position doesn't change," Lyman told AFP.

The ICC first charged Bashir with war crimes and crimes against humanity in 2009. The court added three genocide charges in July 2010.

"Irrespective of this, we seek a better relationship with the government of Sudan, which is possible," said Carson, adding that Washington could also seek to have a higher level of diplomatic representation in Khartoum.

Currently, Washington is represented in in Khartoum by a charge d'affaires and a deputy chief of mission.

"We look to have a normalized relationship with a government in Sudan, notwithstanding the need for President Bashir to answer the charges leveled against him by the international community and the ICC," said Carson.

Western powers have raised new concerns in recent months about the conflict in Darfur, in western Sudan, where the UN says at least 300,000 people have died since rebel groups took up arms against Bashir's Arab-dominated government in 2003.