America's chief military officer says the Soviet Union has yet to reform its armed forces into a defensive posture but that the United States must be patient in its push for the change.

Adm. William Crowe, chairman of the Joint Chiefs of Staff, said in an interview on Thursday that Moscow has not taken the steps Washington would like to see despite Soviet leader Mikhail Gorbachev's talk of changing from an offensive doctrine.At this week's Red Square celebration of the 1917 Bolshevik revolution, Soviet Defense Minister Dmitri Yazov clearly endorsed for the first time in such a major forum the principle of reasonable sufficiency for Soviet defenses and the defensive doctrine promoted by reform-minded Gorbachev.

But Crowe was dubious.

"The kind of evidence the U.S. military wants to see is alteration of investment policy, in (arms) production and in forward deployments, and as yet I have not seen that," he said in the interview with Reuters and the international television agency Visnews.

"On the other hand, we may be too impatient. In all fairness to the Soviets, to do these kinds of things will take time. They are changing major policies and in another sense they are changing the culture of the Soviet military. You don't do that abruptly and quickly, if you do it at all."

Crowe said his advice was: "First we should be patient and watchful, and secondly, wary."

The admiral voiced optimism for the prospects of reaching a superpower treaty on reducing strategic nuclear weapons and said he believed both Washington and Moscow were in agreement on preventing the proliferation of atomic weapons to underdeveloped nations.

Crowe, asked if the United States will be able to maintain its forces in Europe at a current level of about 340,000 troops over the next few years, said: "It is not obvious that we will if we have to face decreasing military budgets."

Military planners fear Congress will try to make cuts in the Pentagon budget to help slash the huge federal budget deficit.

Analysts have said if Congress does not at least allow for increases in inflation over the next five years planned defense programs could face shortages of over $400 billion for that period.

Crowe said he believed President-elect George Bush would help fight military spending cuts and would be supportive of the Defense Department as President Reagan has been.

"On the other hand, let me say that campaigning for the presidency and being the president are two different things. Mr. Bush on Jan. 20 will be thrust into the real world in a very dramatic way."

A top priority for Bush will be to decide whether to continue Reagan's push for mounting 10-warhead MX missiles on rail cars or developing a single-warhead mobile "Midgetman" strategic missile mounted on its own truck launcher.

"If, in fact, we have to live with a decreasing budget for several years, the president will be confronted with some extremely difficult decisions," Crowe said.

He said one problem was growing unrest in Washington at the perception U.S. allies are not doing their utmost to support defense in their areas of the world.