President Reagan isn't buying the House and Senate intelligence committees' proposals for preventing another Iran-contra affair, including a required 48-hour notice to Congress of any covert action, CIA Director William H. Webster said yesterday.

Webster said the proposals would tie a president's hands in cases where a premature leak could cost lives, and when a foreign intelligence service with vital information insists that Congress not be told.

A 48-hour notification requirement would "promote tension" between Congress and a president "for years to come," Webster added.

The CIA director told a House intelligence subcommittee that a recent presidential directive would make certain all but the most extraordinary covert activities would be promptly reported to Congress.

In any rare case where the president ordered a delayed notification, a top-level policy group would review the decision every 10 days, Webster said.

Some lawmakers have suggested that they might have persuaded Reagan not to sell arms to Iran had he notified the intelligence committees or congressional leadership of his plans. Notification of Reagan's approval was withheld from Congress for 10 months in 1986, until U.S. negotiations with Iran were disclosed by a Lebanese publication.

The administration has already lost round one in its battle to maintain greater discretion on when to notify Congress. The Senate intelligence committee voted 13 to 2 for legislation that includes the 48-hour requirement. It is similar in other respects to the House bill Webster is trying to derail.

"A bill which fails to preserve the flexibility and authority the president needs to conduct intelligence activities effectively will not be acceptable to the president," Webster said. He did not say specifically whether Reagan would veto such a measure.

Current law requires an administration to give the intelligence committees or eight top congressional leaders prior notification of significant intelligence activities. But it allows the president to delay in extraordinary circumstances, and issue the notification in "timely fashion."

Webster said there have been only three instances when timely notification was not given: the Iran-contra affair, the rescue of Americans from Iran who were hidden by Canadian diplomats and the failed military attempt to rescue American hostages in Iran.