The Reagan administration said yesterday that it will ask Congress to approve new arms sales to Saudi Arabia, but it added that no decisions have been made on the precise nature and timing of the request.

"There are a number of weapons sales to Saudi Arabia that we are considering, and will be sending to Congress at some point," White House spokesman Marlin Fitzwater said in Santa Barbara, Calif., where President Reagan is vacationing. "Discussions have been held with members of Congress about the best way to present this package . . . but no decisions have been made at this point."

Fitzwater was reacting to a Washington Post report yesterday that the administration is planning a $1 billion sales package that would include 12 to 14 F15 jet fighters and 1,600 Maverick antitank missiles whose sale was withdrawn in June by the administration because of congressional opposition. The Post said the administration was expected to begin notifying Congress soon after it returns from summer recess on Sept. 9.

Fitzwater acknowledged that the total value of the various weapons systems that the administration would like to provide to the Saudis is about $1 billion. In regard to the timing, he said some in the administration think September might be too early, adding that "it could go later in the year."

Other administration officials, speaking on condition that they not be identified, said the sales package described by The Post had been worked out recently by an interagency planning group under the direction of the National Security Council. However, they continued, while it has been presented to the White House as a formal recommendation, it has not yet been approved by Reagan.

These sources said that some officials, including White House chief of staff Howard H. Baker Jr., are hesitant about exposing the president to an embarrassing new political defeat and want to take more soundings about the depth of congressional opposition before seeking to push through an arms sale of the size contemplated.

But, the sources added, other officials, centered in the State Department and Pentagon, believe that the Iran-Iraq war has increased the urgency of strengthening Saudi Arabia's ability to protect Persian Gulf oil supplies. In their view, even if a congressional defeat seems likely, the administration should seek to make the sale as a gesture of its support for the Saudis.

If that view prevails, the sources said, notification almost certainly would have to be made in September to allow sufficient time for the required consultations with Congress before the end of its current session, which could come as early as October. Otherwise, the sources said, the request would have to be deferred to sometime next year.

"If the decision is made to treat the sale as a matter of urgency, then the timing of notification will be determined by Congress' legislative calendar, and that means September," said one official.

Sen. Claiborne Pell (D-R.I.), chairman of the Foreign Relations Committee, said he understood that a formal sales proposal would not be made soon.

Pell recalled that he wrote to Reagan last month urging a "moratorium on proposals for further major arms sales to Saudi Arabia until the administration has reevaluated plans and programs with that nation in close consultation with the Congress."