Numerous senators elbowed for position in the devate over SALT II yesterday as the Senate completed business and began its August recess.

Twelve senators signed a letter to President Carter advising him that they were "gravely concerned" over attempts by some colleagues "to tie arms procurement to arms control" by holding SALT II "hostage" to increased defense spending.

Linkage between approving SALT and spending more on arms- -an idea proposed by several key senators- -is "an unacceptable price to pay," these senators wrote.

Most of the signers were liberal Democrats, but they were joined by Larry S. Pressler (R-S.D.) and Lowell P. Weicker Jr. (R-Conn.).

Former president Gerald Ford has joined those calling for expanded defense commitments as a precondition to approving SALT. In an interview with Jack W. Germond and Jules Witcover of the Washington Star, Ford said he favored an expanded defense program costing about an additional $10 billion per year, and would oppose approval unless the Carter administration takes strong action.

At the other end of the spectr!m, a sharp critic of the treaty, Sen. Ernest F. Hollings (D-S.C.), called a news conference to denounce talk of linking SALT and arms spending as "a charade which seriously jeopardizes our country."

Hollings charged that "senators see a political way out of their dilemma by saying they will vote for defense later if they can vote SALT now." In fact, he said, senators aren't really ready to raise defense spending. He noted that on Thursday the Senate Budget Committee voted against a proposal to meet the Carter administration's commitment to raise defense spending in real terms by 3 precent next year.

Hollings promised to introduce an amendment to the budget resolution next month that would add $2.6 billion in defense outlays to meet that 3 percent target.

"Even Italy's got the 3 percent," Hollings said in an interview. "Canada's up to 4.8 percent. France. . . is over 6 percent."

At the White House. press secretary Jody Powell said that President Carter welcomed the debate over defense commitments and SALT II as "healthy and constructive," but that Carter could not "make defense decisions in terms of trading for votes" on the treaty.

In another development, the chairman and the ranking Republican on the Senate Foreign Relations Committe, Frank Church (D-Idaho) and Jacob K. Javits (R-N.Y.), announced that they would jointly introduce a package of alterations to the treaty.

They released these recommendations yesterday at a news conference whosn contents were "embargoed" for publication on Sunday. The Washington Post chose not to accept these ground rules and obtained information on the Church-Javits proposals from other sources.

The two senators suggested that the Senate amend its "resolution of ratification" to SALT II to add the following:

A reservation declaring legally binding the oral Soviet pledge given at the Vienna Summit meeting to restrict production of the controversial Backfire bomber to 30 planes per year.

An understanding that the United States retains the right to give its allies "nuclear and conventional weapons required for their common defense under SALT II.

An understanding that the prototol to the treaty, which limits U.S. cruise missile deployment, cannot be extended beyond its expiration at the end of 1981 without a two-thirds vote of the Senate.

As Church and Javits pointed out, these are "consensus" proposals that have already gained wide approval in the Senate. All of them were proposed by Sen. Joseph R. Biden Jr. (D-Del.) on the second day of SALT hearings.

Biden yesterday announced his support for the treaty, rejecting what he valled the "mindless machismo" of hardline treaty critics and warning against "a symbolic strategic splurge" as the price for the treaty.

Sen. Jake Garn (R-Utah) yesterday issued a statement praising opponents' contributions to the treaty debate and predicting that the Senate will significantly amend the accord this fall. Sen. Barry Goldwater (R-Ariz.) issues a statement saying "there is no way in the world" he could ever vote for SALT II. CAPTION: Picture, Sens. Larry Pressler (R.S.D.), Howard Metzenbaum (D. Ohio), Adlai Stevenson (D Ill.) and Donald Riegle (D. Mich.), from left, voice their concerns that SALT II might be held "hostage" to increased defense spending. By James K. W. Atherton-The Washington Post