SANTA BARBARA, CALIF., NOV. 25 -- President Reagan will insist that the Senate ratify the intermediate-range nuclear forces treaty in its existing form without amendments or reservations, including those expected to be offered by conservative Republicans seeking to block the pact, White House chief of staff Howard H. Baker Jr. said today.

Speaking to reporters here after he and acting national security adviser Colin L. Powell met with Reagan at his mountaintop ranch to discuss the forthcoming summit and other issues, Baker said, "It's Ronald Reagan's treaty. So I'm sure that the president will be anxious for the Senate to ratify this treaty in this form because he negotiated it."

Baker added that Reagan had set down the negotiating instructions and, despite initial Soviet rejection, had persisted with the idea of eliminating an entire class of weapons.

"I was in the Senate long enough to know, obviously, that members may have amendments or reservations or understandings that they may offer and that under the rules of the Senate you can do that," added Baker, a former Senate majority leader.

"But I fully expect it will be the administration position that this treaty is the best treaty that can be negotiated with the Soviet Union -- that it's good for the security of the United States and it ought to be ratified in the form in which it was negotiated."

The treaty to eliminate medium-range and shorter-range nuclear missiles in Europe is to be signed at next month's summit between Reagan and Soviet leader Mikhail Gorbachev in Washington. Baker's comments came in response to questions about a possible bid by Senate conservatives to modify or kill the treaty by seeking to amend it or attach new reservations during the debate, which is expected to begin early next year.

Baker said Reagan is "gonna go full bore" in a campaign for the treaty. While predicting that the treaty "will be very attractive and very appealing to the vast majority of senators," Baker acknowledged that some conservatives "are very concerned about this treaty or any treaty with the Soviet Union and many of them are especially concerned about verification."

"I don't know what particular techniques will be employed to try to remove the concerns of individual senators but I remain convinced that on balance the value of this treaty and the nature of verification {procedures} make it attractive enough so that it will be ratified by the U.S. Senate," Baker said.

While backed by many Democrats, the treaty has met with vocal opposition from some Republican presidential candidates, and Senate Minority Leader Robert J. Dole (R-Kan.) has expressed lukewarm support for the pact. A senior White House official said today that Dole may attempt to offer a reservation seeking to improve on the verification measures as part of his overall campaign strategy to demonstrate a hands-on ability to deal with issues.

Baker said he intends to make a "special effort" to brief and consult with Dole and other Senate Republicans. Asked whether Reagan would meet with conservatives before signing the document, as Sen. Steve Symms (R-Idaho) urged today, Baker said Reagan would meet with senators before and after the signing, now set for Dec. 8, the first day of the summit. The first meetings are set for next week, he said.

"Stopping a treaty is not as easy as you think," Baker said. "A treaty is a very different situation than the ordinary legislative encounter." For example, he noted, the majority leader can bring it up on a nondebatable motion, "so you eliminate at least one filibuster there."

"It takes more votes to ratify a treaty -- two thirds -- than it takes to shut down a filibuster. So the dynamics of that situation are somewhat different," Baker said. "It has been my experience over the years that if the leadership really wants to push for a treaty and push it to a vote, they could do that. And it is also my impression that both the Republican and Democratic leadership of the Senate do want to see this matter presented to the Senate and to do so in a prompt way."

Describing the treaty as a "major achievement" that "has never happened before since the dawn of the nuclear age" because it eliminates weapons, Baker said INF ratification could move forward while talks continue on reducing strategic weapons. Baker said it would be "foolish in the extreme" to wait.

Baker also said Gorbachev would have a scaled-down meeting with members of Congress. Baker said Reagan and Gorbachev will hold televised news conferences, but a White House aide later said Reagan will deliver a speech, not take questions at a news conference, shortly after Gorbachev departs.

Senate reaction to the INF announcement illustrated how the treaty has divided Reagan's party.

Symms urged Reagan to review details of the pact with Senate conservatives -- his "best supporters in the Senate" -- before signing it.

While not saying he would oppose the treaty, Symms raised serious questions about verification provisions and other details and suggested unwise concessions may have been made under pressure to reach an agreement in time for signing at the Reagan-Gorbachev summit.

But the reaction from less conservative Republicans was more favorable. Sen. John W. Warner (R-Va.), while not endorsing the treaty, called it a "landmark achievement by this administration" and said U.S. negotiators believe "we got more in the verification area than we anticipated."

Sen. Rudy Boschwitz (Minn.) hailed the agreement as a "huge step toward a long-term, peaceful relationship" and said he is "leaning toward" voting for it.

Staff writer Helen Dewar contributed to this report from Washington.