The U.S.-Soviet arms control agreement President Carter is championing took fire from a new quarter yesterday as Sen. Mark Hatfield (R-Ore.) termed it "another one of those escalating steps in the nuclear arms race."

Hatfield, who has been a leading Senate advocate of arms control, said he is "certainly leaning" toward voting "no" when Carter sends the strategic arms limitation treaty (SALT) to the Senate for approval.

In contrast to the previous attacks from conservatives who complain that SALT II would freeze the United States into strategic inferiority, the liberal Hatfield contended the treaty would "stimulate production" of new weapons.

The United States and the Soviet Union would race to reach the maximum levels of nuclear weapons allowed under the treaty, including missiles suitable for destroying the other nation's offense, Hatfield said.

He expressed these and other concerns about the proposed treaty in an interview to be printed this week in the magazine Sojourners, published by a religious fellowship with headquarters in Washington. The magazine released an advance text to The Washington Post.

The MX missile, which the Carter administration is developing to replace Minuteman ICBMs, is "specifically allowed under SALT II," Hatfield said. "Its increased accuracy would give the United States the potential by the 1980s to destroy Soviet land-based missiles. This threat would prompt the Soviets to take countermeasures, escalating the arms race to still more dangerous levels."

Hatfield also contended that the cruise missile allowed under SALT II is so easy to deploy in quantity on land and at sea that "it poses unique problems for arms control in the future."

He said the proposed treaty is further flawed because it doesn't outlaw guidance improvements that would give nuclear warheads "absolute accurace -- and this is needed only for a first-strike capability."

The search for ways to find and destroy submarines would continue unabated under SALT II. Hatfield said. The United States already is far ahead of the Soviet Union in antisubmarine-warfare technoligy, he added. Allowing further improvements "heightens Soviet anxiety over U.S. intensions and makes the possibility of future arms control far more complex."

He said SALT II "confuses matters" because it is being portrayed as limiting strategic arms without really doing so, making it harder to achieve "some real and valid arms control program.

"Rather than blindly fall into a SALT II treaty," he continued, "we had better let SALT II fade out, and then commit ourselves to an approach that truly would be a move in reversing the arms race."

Hatfield said it would be "presumptuous" of him to decide which way to vote before a treaty was actually before him, but "I am certainly leaning more negatively than positively on the whole issue."

Hatfield said he made public his concerns to signal the Carter administration that "here is one liberal who cannot be taken for granted."

He said the administration has been making concessions "to conservative forces" to improve prospects for ratification, "but there are others besides muself on the so-called liberal wing of the political spectrum who are increasingly concerned" about a treaty which threatens to spawn "a whole new generation of nuclear weapons...."