Gen. Alexander M. Haig Jr., recently retired NATO commander, yesterday proposed that the SALT II pact be held in abeyance until the Carter adminstration make firm commitments to a comprehensive expansion of the U.S. defense effort, and until the Senate resolves "flaws" in the treaty.

Testifying before the Senate Armed Services Committee, Haig declined to recommend rejection of the treaty, and in his prepared statement he said the treaty could be "an instrument which marks the turnabout of a perceived period of drift in the United States leadership."

But during a recess he told reporters that "as of today I could not go along with SALT II," and in testimony he repeatedly criticized the treaty, and, more bluntly, adminstration defense policies.

Haig testified that the NATO allies support SALT II because they believe in arms control, do not want to weaken the American presidency and want to preserve detente. But, he added, "We as Americans can take no comfort" from this support, because it is based on "serious doubts about American leadership today."

Europeans, Haig said, are fearful that if SALT II were rejected and the United States were later challenged by the Soviet Union, America might trade off European interests in Berlin or elsewhere to mollify "an aroused Soviet Union."

Later Haig said Europeans should be even more alarmed: "How concerned will they be in the early '80s," he asked, "when they realise that we have negotiated ourselves into fundamental inferiority?"

Haig agreed with Sen. Gordon J. Humphrey (R-N.H.) that the NATO allies how see the United States as about half as reliable an ally as it was 10 years ago. Sen. John C. Culver (D-Iowa) intervened to ask if Haig meant that the UnitedStates really enjoyed such a good reputation with its allies in 1969, "at the height of the Vietnam war."

Culver said it was his impression that "under your stewardship," NATO cooperation has improved substantially, and that relationships within the alliance are much better than they have been in many years.

"Yes," Haig replied, "That has been a very constructive aspect of American policy." He said the picture is contradictory.

Haig retired from the NATO caommand last month, and this was his most substantive public comment since. He had originally asked that he not be called to testify until former secretary of state Henry A. Kissinger had made his views known. Kissinger is scheduled to testify to the Foreign Relations Committee Tuesday. But Armed Services asked Haig to testify yesterday.

There have been recurrent but unconfirmed reports thatHaig is considering a political career, and some of his testimony yesterday fits that scenario. Several times he changed the ordianry, calm tone of his voice to make points in dramatic, hoarse tones, for example, "You know, the American people just don't want to be second."

Numerous senators tried to get Haig's recommendations for specific changes that might be made in the treaty, but he persistently declined to suggest any. That, he said, is the business of the Senate. At one point he said he had "read the treaty with some haste," and wasn't fully familiar with all its details.

Haig did purpose that the protocol to the treaty, which limits the deploymen of U.S. sea-based and land-based cruise missiles until the end of 1981, must be terminated at the time so that cruise missiles can be used effectively to bolster NATO's nuclear arsenal.

Sen. Gary W. Hart (D-Colo.) extracted from Haig agreement that on a number of specific points SALT II puts stricter limits on a Soviet strategic forces than did the Vladivostok accords negotiated in 1974 by Gerald R. Ford.

Sen. Hency M. Jackson (D-Wash.) then observed that the Soviet threat has become vastly more grave since 1974, so that Hart's comparison had no significance. Haig agreed. CAPTION: Picture, Alexander M. Haig Jr.: "As of today I could not go along with SALT II." By James K.W. Atherton - The Washington Post