The new U.S. special envoy to Sudan said Saturday Sudan's Darfur region is "on the brink" of a deeper crisis.

Scott Gration said after visiting the Zamzam refugee camp in northern Darfur, water and health care are two of the most pressing needs.

Sudanese President Omar al-Bashir expelled 13 foreign aid groups last month after an international warrant was issued for his arrest for alleged war crimes.

Gration reached out to Sudanese humanitarian groups to step in and called on Sudan to allow other groups from Arab nations to come into the region to offer aid.

The Darfur region has been ravaged by nearly six years of civil war that has killed at least 300,000 people and displaced more than 2.7 million.

Gration arrived in Sudan on Thursday on his first visit since being appointed special envoy last month.

He said it will be up to the Sudanese government to determine how it wants to continue with the relationship with the U.S.

Some information for this report was provided by AFP, AP and Reuters.