Critics of SALT II on the Senate Armed Services Committee yesterday pressed Defense Secretary Harold Brown on imbalances and omissions in the new treaty, suggesting that it is unfair to the Unites States.

It was harsher critism of SALT II than Brown heard earlier from the Foreign Relations Committee, but few new points were raised, and Brown disputed the critics, invoking analyses and statistics to argue that the treaty is fair and useful.

Sen. Henrt M. Jackson (D-Washing.), author of a congressional resolution adopted in 1972 that said SALT II should provide for equal Soviet and American strategic forces, yesterday told Brown the new treaty fails to meet that standard. Brown disagreed.

Sen. Gary Hart (D-colo.), a supporter of the treaty, elicted from Brown the prediction that the Soviet Union might deploy 13,000 to 18,000 nuclear bombs by 1985 if SALT II is rejected, 10,000 of them on systems accurate enough to destroy U.S. landbased missiles in their silos. With the treaty, those numbers would be 9,500 and 6,000, Brown said.

Hart said the figures demonstrated the value of the treaty. He challenged critics to show how the Soviet threat could be reduced by rejecting the treaty, or what U.S. strategic programs were prohibited by the pact.

But the critics on the committee declined this challenge, concentrating instead on specific aspects of SALT II that they think favor the Soviet Union. This was the theme Jackson Key-noted with his charge that the new treaty fails to meet the test of his 1972 resolution calling for equality.

The resolution called on the executive branch to negotiate a SALT II that provided for equal lavels of intercontinental strategic forces. SALT II does provide that both sides can have 2,250 strategic weapons launchers in 1982.

Jackson said floor debate in 1972 showed that the Senate wanted equality "taking account of throw-weight" -- the payload each superpower's rockets can deliver to the territory of the other. SALT II permits the Soviets to maintain a large lead in this category.

Brown responded that SALT II granted the Soviets some advantages, which he said balanced out, leaving an equal agreement. Jackson rejected that view.

"a team of giants and a team of dwarfs might have equal numbers of players . . . but they are hardly equal," Jackson said. Brown later replied: "if the dwarf are just as strong and agile and able as the giants, that's an unequal situation."

Later, Sen. John C. Culver (D-Iowa) contended that the Soviets' throw-weight advantage was largely neutralized by SALT II's limits on the number of individual wareheads or nuclear weapons that could be placed on a single rocket. These limits prevented the Soviets from taking full advantage of their heavy rockets and superior throw-weight, Culver said.

Sen. John W. Warner (R-Va.) raised a new point in the hearings when he asked Brown about 75 older Soviet submarines that carry about 300 short-range cruise missilels, of pilotless drones.

Couldn't these be used to attack coastal cities in the United States with lethal effect, Warner asked? Brown said that hypothetically they could, but that the submarines in question were deployed for use against shipping at sea, not land targets. He noted that the Soviets one deployed these old submarines near American castlines, but dropped that once they had their own submarine-launched ballistic missiles, which could better be used to attack the American mainland.

Culver later said that those Soviet submarine missiles were comparable to an American model from the 1950s that can now be found only in "the navel museum."

Several senators pressed Brown on the Treaty's failure to cover the Soviets' mdium-to-lond range Backfire bomber. Brown repeated that the Backfire, like U.S. nuclear weapons based in Europe and the Soveits' "heavy" supermissiles, was one of the areas removed from the treaty in a series od compromises.

Sen. Barry Goldwater (R-Rriz.), one of the senators who raised the Backfire issue, revealed yesterday that he has now been satisfied that verification of SALT II is not a major problem. Goldwater is a senior member of the Intelligence Committee.

Sen. Sam Nunn (D-Ga.). whose vote on SALT II is regarded as crucia, failed to tip his hand yesterday, using his questioning time to query Brown on defense issues not specifically covered by the new treaty. Committee Chairman John C. Stennis (D-Miss.), another key vote, was friendly to Brown and did not reveal his feelings about SALT II. CAPTION: Picture 1, Defense Secretary Harold Brown defended SALT II before its critics on the Senate Armed Froces Committee yesterday. By James K. W. Atherton -- The Washington Post; Picture 2, Sens. Goldwater, left, and Warner confer before start of SALT hearings. AP