By R. Hart Phillips
Special to The New York Times

HAVANA, July 6--Insistence by the Cuban rebels that Ambassador Smith deal directly with them for freeing of the remaining American captives is the cause of the delay in the release of the prisoners.

This was learned today from an unimpeachable source known to be in the confidence of the rebel high command.

"We do not want the United States to intervene in the internal problems of Cuba," a prominent member of the Opposition said.  "But we do want the American Government to be neutral."

"As we have already advised the American Ambassador, we are not satisfied with the representation of the United States Consul Park Wollam," the Opposition spokesman said.  "Mr. Park Wollam is a gentleman for whom we have the highest regard but we insist on discussing this matter with American Ambassador Smith personally.

"We want to request that the United States Government maintain the strict neutrality which it advocates, which we believe include the prohibition of any military or monetary aid to Batista and at the same time we would like to express to him our feelings of friendship for the United States."

The Cuban Government, rebel sources said, has refrained from its customary bombing in the mountain areas of Oriente for the last few days not to endanger the lives of the Americans held captive.

The reports that Raul Castro, leader of the rebels in the northern part of Oriente Province, kidnapped the Americana and Canadians without authorization of Fidel Castro, his brother, and leader of the rebel movement, is discounted by Opposition sources here.  They say there is no rift or lack of harmony between the two brothers.