UPDATE 4-Nigerian rebel Okah could be freed early this week

* Gov't to withdraw case against rebel leader on Monday

* Some rebels say they will lay down arms after Okah release

* Analysts doubt violence will subside in Niger Delta

(Adds comment from presidential aide)

By Hannington Osodo

LAGOS, July 12 (Reuters) - A top Nigerian rebel leader is expected to be freed early this week, his lawyer said on Sunday, but analysts doubt his release will lead to a significant drop in militant attacks in Africa's biggest oil sector.

Henry Okah, suspected leader of the Movement for the Emancipation of the Niger Delta (MEND), agreed to terms of a federal amnesty programme at the weekend and the government has promised to release him after more than a year in detention.

A presidential aide who attended the meeting with Okah's lawyers told Reuters the government would on Monday formally withdraw its case against the rebel leader, who is on trial for gun-running and treason.

Although some militants have said they would lay down their arms if Okah is released, analysts believe violence in the Niger Delta will not subside.