Next week’s planned referendum in Sudan on the political future of Darfur “cannot be considered a credible expression of the will of the people” given the circumstances, according to a statement issued by the U.S. State Department on Saturday.

Rebels have sought a referendum on whether Darfur should be declared an autonomous region but plan to boycott next week’s vote because of an upsurge in fighting and questions about whether and how those displaced in the more than decade-old uprising will vote.

Darfur was an independent sultanate for several centuries before it was incorporated into Sudan in 1916. The region is divided into five states, which the ruling National Congress Party says is a more efficient way to run the country but opponents say gives Khartoum too much power.

The U.S. State Department statement noted those living in displaced-persons camps effectively will be disenfranchised, as will Darfuris residing outside the region.

“The United States expresses serious concern regarding the government of Sudan’s plans to conduct a referendum on April 11-13 over the political future of Darfur,” the statement said. “If held under current rules and conditions, a referendum on the status of Darfur cannot be considered a credible expression of the will of the people of Darfur. Moreover, it will undermine the peace process now underway.”

The statement noted the only way to resolve the Darfur conflict is through a political process that “secures a lasting cessation of hostilities and creates the space for meaningful participation of Darfuri groups and all Sudanese in an inclusive and genuine national dialogue,” adding the referendum undermines both goals.

bashir Sudanese President Omar Hassan al-Bashir addresses the crowd during a campaign rally in East Darfur, April 5, 2016. Photo: Mohamed Nureldin Abdallah/Reuters

The three-day vote likely will uphold the five-state system and comes amid increased fighting. Middle East Eye said rebels plan to boycott the vote, although they support the concept of a referendum.

Iran’s semiofficial Press TV reported fighting has forced 138,000 people to flee their homes in Darfur since mid-January, joining the ranks of 2.5 million who have been displaced over the life of the conflict, and the Sudanese government has blocked U.N. peacekeeping forces and humanitarian organizations from conflict zones.

“It is the people of Darfur who choose whether they want states or one region, and we are holding this referendum so that no one else can come and say we want this or that,” President Omar al-Bashir, who is wanted by the International Criminal Court on charges stemming from atrocities in Darfur, said last week following a visit to the area.

China’s official Xinhua news agency reported the visit to the five state capitals was designed to legitimize the referendum, which Khartoum had hoped would lead to an end of a U.S. trade embargo in place since 1997.

“In most of his speeches in Darfur, al-Bashir reiterated that the security situation generally was stable and that the army was ready to clear what have remained of small pockets where rebels are still present,” Taj-Eddin Adam, a prominent Darfuri politician, told Xinhua. “This was a clear message that the government was pressing ahead with the military option, particularly after the Darfur rebels refused to sign a road map agreement recently proposed by the African Union mediation in Addis Ababa, Ethiopia.”