Sen. John Glenn (D-Ohio) announced yesterday that he will vote against sending SALT II from the Foreign Relations Committee to the Senate floor, but that he still hopes to support the strategic arms limitation treaty when a final vote comes late this year or early next.

Glenn's announcement means the committee is likely to approve the Soviet pact by 9 to 6 or perhaps 8 to 7 when it takes a vote, perhaps today.This is less than the two-thirds margin that will eventually be needed for full Senate approval. Pro-SALT senators and administration officials expressed confidence that the committee margin would not determine the final outcome.

The committee's markup has bogged down again, this time because of the addition of a new staff consultant, retired Maj. Gen. Edward J. Rowny, former representative of the Joint Chiefs of Staff on the SALT delegation in Geneva.

At the urging of Sen. Jesse HELMS (R-N.C.), Rowny was hired by the Republican minority on the committee as a $143-a-day consultant. Yesterday Helms asked Rowny for extended comments on several issues, and apparently plans to continue asking for his advice in the final stages of the markup.

Rowny is using this opportunity to repeat anti-treaty arguments raised earlier by himself, as a witness before the committee, and by other critics.

This has exasperated some Democrats on the committee and apparently delighted Helms.

Asked yesterday about Rowny's presence, Sen. Edward Zorinsky (D-Neb.), who has often voted with treaty critics on the panel, said: "At $143 a day, I thought we'd get a little more persuasiveness."

In an interview Zorinsky declined to say how he would vote, but predicted the committee would approve 11 to 4 or 10 to 5.This was before Glenn's announcement. The only way to arrive at such a count would be to included Zorinsky as a treaty supporter, since four Republicans have lined up against it.

Yesterday the committee voted 8 to 7 against a proposal by Helms to amend the treaty by limiting both countries to reserve stockpiles of no more than 200 missiles beyond the number of missile launchers permitted by the treaty. Helms said the Soviets might hide a large and dangerous quantity of missiles without this restriction.

Glenn explained to reporters yesterday that he could not now vote for the treaty because the United States has not yet been able to find new methods for eavesdropping on Soviet missile tests to compensate for the loss of electronic spy stations in Iran.

However, Glenn, added, "Things are developing rapidly in this area and it's entirely possible that I can vote no in the committee and yes on the floor . . . I'm very hoepful, in fact I'm optimistic" that new technologies will be in place before the final vote, he said, and if they are "I will vote yes."