The administration, following a series of high-level meetings here and abroad, has begun to come to grips with the Polish crisis by pinning the blame increasingly on the Soviet Union.

This is the significance of President Reagan's opening statement at his news conference yesterday, which went much further than U.S. public statements of the last five days in condemning imposition of martial law in Poland and in placing the responsibility on Moscow.

The statement also went much further than previous public utterances by most of the European allies. Only French President Francois Mitterrand, joined yesterday by British Foreign Secretary Lord Carrington, has taken a strong public position, and diplomatic exchanges to this point are reported to show little sign of a unified allied position.

In the first several days after the sudden crackdown in Poland, the principal concerns of senior U.S. officials were to avoid any word or deed that might create false expectations among the Polish people or be cited by the Soviets to justify an open and all-out intervention. These concerns remain.

As events have unfolded in Poland, however, the very murkiness of their motivation led to another concern: that the Soviets might be able to manage a remote-control suppression so unclear in its origins and uncertain in its aims that the West could not define or counteract it.

Such a possibility, even more than open Soviet intervention, is seen by Washington policy-makers as the "worst-case scenario" for Polish events.

Secretary of State Alexander M. Haig Jr. told members of the Senate Foreign Relations Committee over lunch yesterday, according to participants, of his belief that the Polish crackdown was long in the planning, not an action taken because of last weekend's Solidarity union resolutions in Gdansk.

Haig said he could not confirm reports that the Soviet Union had given an ultimatum to Poland's Gen. Wojciech Jaruzelski to crack down or face Soviet intervention, but he left no doubt that he considers the Soviets ultimately responsible.

Haig is also reported to have forecast that even if Soviet force is applied directly in Poland, Soviet divisions are not likely to pour across the borders in a dramatic and open fashion that would unite the West and the rest of the world in reaction.

More likely, the senators were told, would be a mildly worded request for Soviet help from Warsaw's leadership and an almost imperceptible increase in involvement of the three Soviet divisions stationed in Poland.

For the allies, especially, the question of the Soviet role is crucial to the question of counteraction.

Most of the attention in the two earlier rounds of top-level NATO discussions about Poland, in December, 1980, and last March, revolved around response to open and dramatic Soviet military intervention, according to informed officials. This was the main threat seen then, as Soviet troops appeared to be mobilizing to move.

There was much less attention given then, and no alliance-wide agreements on, a Polish scenario in which the Soviet role is ambiguous. And yet this increasingly seems to be the situation.

From the beginning, Haig and other senior officials made clear, as Reagan indicated yesterday, that major Western levers in the Polish situation are political and economic. Levers of that kind can rarely be wielded effectively by a nation acting alone. They require allied cooperation and coordination.

The Carter administration learned that lesson two years ago in the aftermath of the Soviet invasion of Afghanistan. After jumping out front with its grain embargo, the United States found its allies unwilling to cooperate on additional measures such as clamping down on high-technology exports to the Soviets, and the effort to pressure Moscow by isolating it economically proved unsuccessful.

While it is too early to know if the same thing would happen this time, there is a clearly widening divergence between the kind of strong rhetoric used by Reagan yesterday and the far more circumspect statements of major West European leaders other than Mitterrand and Lord Carrington.

Far more typical has been the wait-and-see attitude adopted by West German Chancellor Helmut Schmidt, whose country has the biggest stake in trade and other financial dealings with Poland and the Soviet Union.

West German participation in an economic offensive against these countries would have severely wrenching effects on German banks, which are Poland's biggest private creditors, and German industrial firms, which have a thriving export business with the East bloc.

One much discussed potential sanction--withdrawal of Western support from Soviet development of a pipeline to carry natural gas from Siberia to the West--could totally disrupt Bonn's long-range plans for its future gas supplies.

If the Polish situation deteriorates, leading to major bloodshed or overt Soviet intervention, West German public opinion almost certainly would force Schmidt's coalition government to take a tougher stance along the lines sought by Washington. For the present, though, Schmidt has signaled quite clearly that he is not about to rush into strong judgments, and until now his position appears to be shared widely in Western Europe.

As more dramatic reports leak out of Poland, European public opinion could shift. Even so, continuing uncertainty about the Soviet role would make a unified response much more difficult.

Now that Reagan has spoken, in his opening statement reportedly drafted in basic form two days earlier, an increasingly explicit U.S. position is to be carried forward by Haig, Secretary of Defense Caspar W. Weinberger and White House counselor Edwin Meese III. All three are scheduled for television interviews this Sunday.