American evangelist and humanitarian leader Franklin Graham has called upon President Barack Obama to immediately appoint a special envoy to Sudan to help resolve the growing threat of chaos there after the International Criminal Court issued an arrest warrant for Sudan’s sitting president.

Graham, who was in Sudan last week, said the United States “must take the lead” in solving the Darfur crisis as well as making sure the Comprehensive Peace Agreement (CPA) is implemented.

The CPA was a peace agreement signed in 2005 by the Sudan People’s Liberation Movement and the Government of Sudan that ended the 20-year civil war between North and South Sudan. In recent months, the SPLM has accused the central government of not abiding by the agreement leading to growing tension between the two bodies that threaten to unravel the peace deal.

Samaritan’s Purse, the Christian relief organisation headed by Graham, has worked extensively in both South Sudan and in Darfur.

Last week, Bashir had expelled the 13 largest aid groups operating in Darfur in response to the ICC arrest warrant that charged him with crimes against humanity in Darfur. Aid groups estimate that the expulsion will threaten the survival of more than two million Sudanese who depend on the aid.

Graham, in a statement Tuesday, urged Bashir to allow humanitarian aid groups back into Darfur.

“I urge President al-Bashir and the government authorities to stop NGO (non-government organisation) expulsions and allow those expelled to return,” Graham said. “The displaced people of the Darfur conflict are in a vulnerable position and urgently need the assistance of those organisations.”

The situation in Sudan appears to be worsening, after the US Embassy in Sudan authorised nonessential staff and family to leave the country earlier in the week. Following the arrest warrant, anti-Western rhetoric has risen sharply along with the danger of violence against Westerners.

The embassy said it has received information of threats against American and European interests in Sudan, according to AP. It also warns Americans to avoid travelling to Sudan.

Both Graham and the president of South Sudan, Salva Kiir, have expressed a strong desire for the United States to be engaged in the peace process of Sudan.