President Reagan is taking some sharp jabs at the Soviets in his run-up to the summit with Soviet leader Mikhail Gorbachev partly to demonstrate that the meeting is not "a session to be taken lightly between old friends" but "a summit between old enemies," White House spokesman Marlin Fitzwater said yesterday.

White House officials said Reagan's use of hard-edged rhetoric on Soviet conduct in Afghanistan as well as his accusation that the Soviets have committed a new violation of the 1972 Antiballistic Missile (ABM) Treaty were intended to show conservative critics that he is approaching next week's meetings with Gorbachev without illusions.

Reagan plans to continue a campaign of what one official described as "laying down markers" this morning when he makes a speech at the Old Executive Office Building on human-rights issues.

One of these officials said Reagan is also engaging in a "preemptive strike" against conservative critics of the intermediate-range nuclear forces (INF) treaty that he and Gorbachev are to sign Tuesday. The official said the president and his chief of staff, Howard H. Baker Jr., had been warned by Senate Minority Leader Robert J. Dole (R-Kan.) and by former senator Paul Laxalt (R-Nev.) that conservatives have more than 20 of the 34 Senate votes needed to block ratification of the treaty.

"Our polls show that rank-and-file Republicans overwhelmingly support the treaty, but that doesn't guarantee a smooth ride in the Senate," the official said. "Reagan's citation of the Soviet violation {of the ABM treaty} should be a signal to everyone that he intends to insist on verification of and compliance with any treaty he signs."

When Fitzwater was asked whether Reagan was setting the proper tone for the summit with his latest speeches and actions, the spokesman said, "we think the climate is exactly appropriate." He also said "the president clearly is trying to address the specific criticisms of conservatives and others who don't believe, for one reason or another, in the INF treaty."

A senior White House official who discussed administration strategy on the condition he not be identified said that "what you've got to do as we're about to sign an arms-control agreement is to demonstrate that there are a lot of other issues that define our relationship with the Soviets, and that includes regional issues and human rights."

The official said it was better for the president to be "open about his views now" and not back away from accusing the Soviets of a treaty violation rather than let it come out after the summit and be accused by conservative critics of having soft-pedaled his stand because Gorbachev was coming.

"We're talking to an American audience as well as a world audience," the official said. "Once the treaty is signed, you've got to get it ratified."

Reagan's rhetoric appears to reflect a continuing concern by White House officials that the president, "I've had a respect for him {Gorbachev} ever since I met him."

-- President Reagan

despite his long-held reputation as the champion of conservative interests, is vulnerable to attacks from his right.

An official said that even if this opposition did not succeed in stopping the INF treaty it has the potential for bringing down more ambitious attempts to secure and ratify reductions in the strategic, or long-range, arsenals of the superpowers. He pointed out that among the Republican presidential candidates only Vice President Bush gives unreserved support to even the INF treaty.

The worries of Reagan's staff about the political vulnerability of arms-control treaties may exceed the president's. Reagan's rhetoric about Gorbachev in off-the-cuff comments, for instance, has been notably softer than the speeches that have been prepared for him.

For instance, when Reagan spoke in Jacksonville, Fla., on Tuesday he gave a prepared speech to high school students that denounced Soviet conduct in Afghanistan as well as Soviet treatment of political prisoners and would-be emigres. He said he will bluntly tell Gorbachev that it is important for him to improve Soviet human-rights practices and to set a date for withdrawal from Afghanistan.

But Reagan also decided, in a departure from his usual practice, to take questions from the students. In his answers he took pains to emphasize that Gorbachev is different from past Soviet leaders in agreeing to remove nuclear weapons and in not proclaiming that his goal is a "one-world communist state."

And when asked by a reporter what he thinks of Gorbachev, the president replied, "I've had a respect for him ever since I met him."

But in remarks prepared for him, Reagan's feelings appear to have been subordinated to the White House fears that he faces trouble with his core constituency.

There are those who think that this strategy could fail by emboldening conservatives to offer reservations and amendments to the treaty.

However, White House officials are hoping that Reagan's strategy of frank talk about the Soviets will instead put conservatives in his corner once again after the summit has ended.