Nas. Picture: Bang Showbiz

Nas has asked a court to enforce his custody agreement with Kelis after accusing his ex-wife of denying him access to their son.

The former couple settled their custody battle over eight-year-old Knight last month, but the 44-year-old singer has claimed he tried to pick up the youngster for a scheduled visit last Friday  and the 'Milkshake' singer began "screaming" at him and wouldn't let him take the child.

Nas wrote in court documents obtained by The Blast: "When I arrived at Kelis's house, she immediately began screaming at me, telling me that I could not take our son. She was so irate I did not know what to do."

While Kelis, 38, specifically asked to have Knight for Passover, there was no special arrangement for the Easter weekend, but Nas would have worked something out if she'd asked beforehand.

And according to the documents, Nas believes his ex-wife thinks their custody agreement is just a "guideline" which she doesn't have to abide by.

He included a text message conversation between them, which at one point quotes the 'Bossy' singer as saying: "The agreement we both agreed on is a guideline nothing more. You said and I quote 'we can make it whatever we need and talk about it I just want something on paper' end quote."

Later in the conversation, the 'If I Ruled the World' hitmaker said he would take Kelis to court.

She replied: "Take me dummy. Take me. Have you not seen I'm not afraid of you anymore!!! ... I will not be intimidated by you and we are going to court anyway.(sic)"

Nas also accused Kelis of stopping him from picking Knight up at school when it's his turn but he doesn't want to make that an issue.

He noted: "I don't want to have a confrontation with Kelis, particularly one at our son's school."

The rapper is seeking an order to enforce the agreement and to sanction his ex-wife for her actions.