Humanitarian aid to Syrians is being held up by a lack of security arrangements despite a Russia-U.S. brokered cease fire deal, U.N. Secretary General Ban Ki-moon said Wednesday.

Ban said he has been in touch with the Russian government urging them to exercise influence on the Syrian government to let the trucks in. He said he has also been in touch with the Americans to get Syrian armed groups to cooperate.

"Twenty truckloads (of humanitarian aid) are ready and they were supposed to deliver them today but unfortunately because of all these arrangements for making sure the security and safety of the humanitarian workers, including drivers, have not been made yet so they are at the border," Ban said. "It's crucially important that the necessary security arrangement should be given so that they be allowed to cross the lines."

Ban said the U.N. hopes to take advantage of the cease-fire deal reached over the weekend after marathon negotiations between U.S. Secretary of State John Kerry and Russian Foreign Minister Sergey Lavrov to "immediately deliver vital humanitarian assistance to Aleppo and other besieged and hard-to-reach locations."

The U.N. estimates there are 5 million Syrians in need of humanitarian aid living in hard-to-reach areas.

Ban said despite the ongoing civil war the U.N. has been delivering aid to 5.7 million people on average per month and air drops have been able to deliver aid to 1.2 million people.