Administration sources said the new plan had been developed not by the White House but by the Justice and Treasury Departments. It was presented to Mr. Reagan, they said, by Attorney General William French Smith at a meeting of the Cabinet Council on Legal Policy on Sept. 25. Asked about it today, however, Associate Attorney General Rudolph Giuliani said, ''It would be premature for me to discuss it now.'' Aims to Prevent Relocation

In a radio speech Saturday, the President was apparently referring to the program when he said he would shortly announce a ''bold, confident plan'' to intensify the war on narcotics. He said it would be aimed at preventing drug traffickers from re-establishing their business in other areas whenever law enforcement shut them down.

''We're going to be waiting for them,'' Mr. Reagan said. ''We're not just going to let them go somewhere else. We're going to be on their tail.''

At another meeting of the Cabinet Council on Wednesday, sources said, the President indicated his interest in going forward with the Attorney General's plan. But the Office of Management and Budget was reported to be raising opposition because of the amount of money required.

''O.M.B. is always looking to keep the outlays down,'' Edwin L. Dale Jr., a spokesman at the budget office said today. ''But I'm not going say what our position is on this one.'' 8 to 10 Cities Chosen