The team had been scheduled to visit Djibouti, Egypt, Eritrea, Ethiopia, Kenya and Yemen, as well as Somalia itself, depending on security there, from 12-25 October.
“The trip to the Horn of Africa region over the Somalia arms embargo has been postponed,” the official, who asked not to be named, told AFP by telephone.
The official has declined to give reasons for the postponement or a date when the UN team is expected to travel to the region.
The team was also due to have examined the ability of countries bordering Somalia to enforce the weapons embargo, first agreed by the UN Security Council in 1992 after two Somali commanders, Ali Mahdi Muhammad and former General Muhammad Farah Aidid, agreed on a ceasefire in the divided Somali capital, Mogadishu.
Aidid has since perished.
Despite the blockade, weapons are still pouring into the ravaged nation.
Rival commanders have accused Ethiopia, Eritrea, Yemen, Djibouti, Libya and Egypt of arming rival factions, a charge that has been denied by the countries.
In April, the UN Security Council adopted a new resolution stating that Somalia constituted a threat to peace and safety in the region, and noted that the weapons embargo had been repeatedly violated.
Somalia has not had a recognised government and has been ruled by clan commanders since dictator Muhammad Siad Barre was overthrown in January 1991.