The United States and the Soviet Union have at least a year to resume arms control negotiations before their new weaponry brings them to the point of no return, according to a report released yesterday by the Carnegie Endowment for International Peace.

"Therefore," the staff report says, "President Reagan and Congress will have a broad range of options to pursue the next step in limiting strategic arms."

Defense Secretary-designate Caspar W. Weinberger said recently that it will take the new administration "a good six months" to prepare itself for arms negotiations with the Soviets.

President-elect Ronald Reagan has rejected the previously negotiated SALT II treaty as lopsided in favor of the Soviet Union, but has said he is willing to try to negotiate a revised one.

Defense Secretary Harold Brown, at a farewell meeting with reporters at the Pentagon Friday, said the arms control process is "so sensible it will survive and resurface even after a period of unpopularity."

"Fundamentally," Brown said in predicting that the Reagan administration will end up pursuing arms control, "it's detente that drives arms control rather than the other way around."

Brown cautioned against resuming the race to perfect an antiballistic-missile system (ABM) for stopping incoming warheads. He said the existing treaty banning extensive ABM defenses should be preserved. Going back into that race, he said, "would be very dangerous to stability" of the nuclear arms balance between the United States and the Soviet Union.

The 139-page Carnegie report, entitled "Challenges for U.S. National Security," assesses options for controling the arms race. The report was prepared by a 26-member panel of specialists.

In discussing Reagan's economic blueprint, calling for increasing defense spending but reducing other government outlays, the panel said that the poor are likely to bear the burden of this policy.

"The Reagan economic program of September 1980 envisions a 9.8 percent cut in nondefense programs in 1985, assuming a 4 percent average annual growth in the gross national product," the panel said.

"If this approach is adopted, the burden of financing increased defense outlays would fall on those citizens who receive government payments -- mostly those in the lower-half income bracket," it said.

Discussing the nuclear weaponry the United States and Soviet Union have deployed, the report said, "It is clear that the United States can retain great confidence in its retaliatory capabilities against the Soviet Union throughout the 1980s. U.S. leaders have every reason to believe that their Soviet counterparts see this the same way."

Because the two superpowers have spent billions to aim vast arsenals against each other, "to the extent that the sky is going to fall, it has largely already fallen," it would take several years before either side could deploy a new strategic weapon that would alter the strategic balance radically.

Although Carter administration leaders have said they developed the new MX missile because the nation's current force of land ICBMs has become vulnerable to sophisticated Soviet warheads, the MX would not be ready for deployment unitl 1986. It is this kind of gap between existing and future weaponry that the panel portrayed as breathing space for a resumption of arms control negotiations.

Leslie H. Gelb, former director of the State Department's Bureau of Politico-Military Affairs and now a senior associate at Carnegie, chaired the panel. Other members included Lt. Gen. Andrew Goodpaster (ret.), former NATO commander Richard L. Garwin, an IBM fellow, and Richard H. Ullman, an international affairs professor at Princeton.