Senate efforts to rewrite the nation's telecommunications laws appeared to fall apart yesterday in a dispute between the chairman of the Commerce Committee and the head of American Telephone & Telegraph Co. over terms of the pending legislation.

In particular, the issue apparently blocking committee action is a provision of the communications bill that would give the Federal Communications Commission the power to monitor closely a proposed modification of AT&T's structure, committee officials said.

"It is highly unlikely this legislation will get back on track until AT&T recognizes that such protections must remain intact if we are to adequately protect consumers and AT&T competitors," said Aubrey Sarvis, chief counsel of the committee.

Sarvis said that there would be no mark-up of the legislation until such an understanding can be ironed out among the chairman, Sen. Howard Cannon (D-Nev.), Sen. Ernest Hollings (D-S.C.) and AT&T on these parts of the bill, "principally on those sections which provide essential protections necessary to prevent unfair practices and monopolistic abuses."

Although consideration of the 13-day-old legislation had been scheduled for last Tuesday, the illness of two sponsors of the bill resulted in a cancellation. Now it is unclear when, if ever, the committee will take up the bill.

Cannon had made his position known to AT&T Chairman Charles Brown in a meeting earlier this week, Sarvis said. "Obviously, the principal authors of the legislation remain hopeful that agreements can be hammered out, but everyone should understand that the bill will not move under the conditions advocated by AT&T," he added.

But not all members of the Commerce Committee see the issue the same way. Sen. Robert Packwood (R-Ore.), the committee's ranking minority member and a sponsor of the bill, said he is willing to take it before the committee "at any time, acknowledging that the outcome may be unpredictable."

"The committee members are capable of wrestling with these complex issues and voting them up or down," Packwood said. "I don't think this legislation should be, or in fact can be, fully orchestrated before the markup."

AT&T, whose executives say communications legislation is needed to insure the stability of the entire industry, continues to say very little about the legislation. Yesterday it only would say it was disappointed with the postponement.

"We share the hope of the bill's sponsors that agreement can be reached and this much-needed legislation with full protections for the interests of consumers and competitors can move ahead speedily," said a company spokesman. Brown was unavailable for comment.

The House communications subcommittee already has passed legislation its advocates say will free AT&T from the provisions of a 1956 consent decree with the government that prohibits the giant company from competing in unregulated communications markets.

Unlike the Senate bill, however, the House legislation -- due before the House Commerce Committee next month -- bars the Federal Communications Commission from tampering with major changes it would make in the phone company's structure.

The Senate bill has similar aims, including the modification of the consent decree, but would permit the FCC to alter the structural changes made in the Bell System.

Meanwhile, an effort by Sens. Edward Kennedy (D-Mass.), chairman of the Judiciary Committee, and Howard Metzenbaum (D-Ohio), chairman of the antitrust subcommittee, to gain an opportunity to review the antitrust consequences of the legislation continued.

But at the same time, the Senate Governmental Affairs Committee, in a letter to Cannon, asked for an opportunity to study the impact the legislation might have on electronic mail. That letter was signed by four committee members including Sen. Abraham Ribicoff (D-Conn.), the committee's chairman.

Critics of the bill, particularly those from the consumer movement and competing telephone concerns, have charged repeatedly that the legislation would hamper the ability of the Justice Department to gain structural relief should the government win its massive antitrust suit against AT&T.

Those parties won support for their position from a surprising source yesterday as former attorney general William Saxbe, who as the nation's chief law enforcement officer in 1974 filed the suit against AT&T, came here to assert that passage of communications legislation would effectively kill the government suit.

"These legislative manuevers are nothing more than a scandalous interference with the judicial process," Saxbe, now a private attorney in Ohio, charged.

"The effect, I fear, will be not to foster a new era of competition so much as it will be to gut the government's pending antitrust case. It would, by statute, foreclose the possibility of a federal court imposing the full measure of remedies the law allows to prevent the recurrence of anticompetitive conduct that may be proved in a court that represents all the people," he said. c

Saxbe, who told a press conference that he represents a group of phone installers who compete with AT&T in Ohio, called the Plea by AT&T for legislation "an end-run around the court.

"More troublesome than curious is the fact that the Congress would unwittingly run AT&T's interference in the abridgement of established legal procedure," Saxbe said.

The Justice Department has stated publicly that so-called "savings clause" in the legislation preserves the status of the antitrust case.