MOSCOW, DEC. 15 -- The Kremlin leadership expects President Reagan to visit Moscow next spring even if a strategic arms treaty is not ready for signing then, a Soviet Foreign Ministry spokesman said today.

"Our great wish," Foreign Ministry spokesman Boris Pyadyshev told journalists, "is that we have that treaty ready by the time President Reagan comes on his visit."

However, the Soviet leadership now has an "even deeper insight into U.S. internal developments," Pyadyshev said in the first press briefing here since Gorbachev returned from three days of talks in Washington last week. The main goal of the summit, he added, should be "general agreement on provisions covering 50 percent reductions to be included in a treaty on offensive arms."

By suggesting that "general agreement on provisions" for a strategic arms treaty would be sufficient for holding the Moscow summit, the Soviet Union appears to be softening the terms under which the meeting -- the fourth between Reagan and Gorbachev -- would be held.

Earlier the Soviet Union had suggested that the main purpose of the Moscow summit would be for U.S. and Soviet leaders to sign a treaty that would cut strategic nuclear arsenals in half and bind both sides to adhere to the 1972 Anti-Ballistic Missile treaty.

"But we have a realistic view of the situation," Pyadyshev said, "and we now have an even deeper insight into U.S. internal developments and the line-up of forces on the American political scene covering arms control issues."

On the eve of last week's summit, U.S. officials said the American position is that a strategic arms treaty would not be a precondition for a fourth summit in Moscow.

The Kremlin leadership appears more eager to set the dates for the fourth summit than it was to set dates for the earlier Reagan-Gorbachev meetings. Asked when the Moscow summit would take place, Pyadyshev said, "Would you be satisfied with, let us say, May or June?"

Pyadyshev also said that the joint statement Reagan and Gorbachev signed in Washington last week ruled out a broad interpretation of the ABM treaty, which restricts research on systems against ballistic missiles such as Reagan's Strategic Defense Initiative (SDI).

Under the broad interpretation, which some senior Reagan administration officials first introduced in October 1985, wide-scale testing of SDI components could take place without violating the treaty.

According to the summit's joint statement, the ABM treaty should be followed "as signed in 1972."

"This means that the two sides have recognized that the ABM treaty must be enforced," Pyadyshev declared, "in the form in which it was signed in 1972, and not in the way it is currently being interpreted in the broad sense by some American interpreters of the treaty."

The Soviet leadership has dispatched a team of Foreign Ministry officials to 44 countries around the world to drum up support for the treaty to eliminate medium- and shorter-range missiles that Reagan and Gorbachev signed in Washington last Tuesday, Pyadyshev said.