For the moment, President Reagan has decided not to play a trump card that would have escalated U.S. charges of Soviet cheating on the 1972 Anti-Ballistic Missile Treaty and left the future of the pact in doubt.

What the White House characterized as a "vigorous discussion" within the administration was resolved Monday in favor of a continued cautious approach to what the president has branded a clear violation of the treaty.With a five-year review of the pact set to begin Aug. 24 in Geneva, the White House repeated its charge that the large Krasnoyarsk radar facility in central Siberia "is a significant violation of a central element of the ABM Treaty."

But the statement stopped short of labeling the radar a "material breach," as some administration hard-liners had advised and which could have allowed the United States to suspend some of its own obligations under the accord.

White House spokesman Marlin Fitzwater said Reagan directed the U.S. delegation to the upcoming treaty review "to make it clear that the existence of the Krasnoyarsk radar violation calls into question the viability of the ABM Treaty and, therefore, it should be dismantled without further delay and without condition."

"Unless removed," Fitzwater said in a reaffirmation of U.S. policy, "the Krasnoyarsk radar violation will force the United States to consider the exercise of its rights under international law to take appropriate and proportionate responses."