The White House says it regrets that Sudanese authorities did not do more to prevent irregularities in the country's national elections earlier this month.
A White House statement issued Tuesday says "inadequacies" in Sudanese preparations for the presidential and parliamentary elections resulted in "serious irregularities." The polls were held between April 11 and the 15.
The White House says political rights and freedoms were "circumscribed" throughout Sudan's electoral process. Some international observers also have cited cases of intimidation and threats of violence.
The statement also said Washington remains committed to supporting Sudan's implementation of a reconciliation agreement between the country's north and south. As part of that deal, southern Sudan is due to hold a referendum on possible independence next year.
Rights groups released a statement Tuesday calling on the White House to take a tougher stance on Sudan's election problems.
Early results in this month's elections show Sudanese President Omar al-Bashir heading toward an overwhelming victory. His main challengers with the Umma Party and southern Sudan People's Liberation Movement withdrew ahead of the election, accusing the government of planning to rig it.
Several Sudanese political parties have accused Mr. Bashir's ruling National Congress Party (NCP) of fraud, including the Beja Congress Party and Democratic Congress for East Sudan.
Members of the two eastern Sudan-based parties told the Reuters news agency they have evidence of NCP activists tampering with ballot boxes. The NCP has repeatedly denied allegations of involvement in fraud.
Sudanese electoral official Abu Bakr Waziri told VOA's English to Africa service there were "minor mistakes" and "technical problems," but that they did not affect the outcome of the elections.
Chinese Foreign Ministry spokeswoman Jiang Yu said Tuesday a Chinese delegation that monitored the elections found them to be "smooth and orderly." Jiang said Beijing will continue to play what she called a "positive and constructive role" in promoting Sudanese reconciliation.
China is a major importer of oil from Sudan and a key international ally of the government in Khartoum.