President Reagan hurled strong words at the Polish and Soviet leaders last night, but he withheld most economic and political pressures for future application if the Polish repression continues.

Nobody would say last night just how long Reagan is prepared to wait before he drops the other shoe. A senior administration official, briefing reporters at the State Department, said the president will be prepared to take the additional steps, including the promised "concrete political and economic measures" toward the Soviets, if remedial steps are not forthcoming in Poland "in a very finite and early period of time."

There was little confidence among American policy-makers that the Polish generals will reverse the flow of power in the near future to resume the movement that they are in the process of busily snuffing out. Rather than projections of success for the American pressures, officials presented an American "obligation" to try such efforts "in the hope they will prevail."

The central reason for Reagan's decision to employ his authority on a phased basis appeared to be desire not to get out in front of the European allies, who may hold more levers of economic and political influence with Poland and the Soviet Union than does Washington.

The small-bore nature of Reagan's announcements regarding Polish fishing, national airline flights and credit guarantees suggests that U.S. leverage toward Poland is limited. Consultation with allies about sales to Poland of high technology was promised, but little of this has been flowing to Warsaw from the United States.

Most of Poland's trade is with Europe, and most of the $26 billion in western loans to Poland is from European banks and governments. Washington's stake, as well as Washington's role, in that Eastern European country is small by comparison.

Though his speech did not dwell on it, Reagan held out a carrot as well as a stick for the Polish leaders, saying that "we in America will gladly do our share to help the shattered Polish economy" if a trend toward democracy is restored. Most of the western aid to Poland in the 16 months since the rise of Solidarity as an independent union came from Europe, however.

The United States has a vital role and tremendous stakes in relations with the Soviet Union, the other nuclear-laden global power. But a series of actions after the Soviet invasion of Afghanistan two years ago has reduced Washington's trade and political leverage to a low point.

Just about all that is left in the economic sphere are the grain sales that Reagan permitted to resume last spring and a long-term phosphate deal. The Soviets have shown that they can purchase grain elsewhere. Their financial credit in the West is important to them, but Europe is the key center for most of this at present.

Reagan's Nov. 18 address, which launched the American side of the Soviet-American negotiations on the limitation of European-based nuclear arms, and which promised early resumption of strategic arms negotiations, gave promise of future accords, and thus was a start on rebuilding American political leverage. But this move on the negotiating front may be imperiled by the deepening dispute over Poland.

The senior official who briefed reporters at the State Department pointed out that the Geneva negotiations on Euromissile limits are in recess until Jan. 12, and said there has been no decision at this juncture to terminate them. The official said these talks have "a unique character and significance," suggesting a desire to protect them if possible.

Again, the greatest significance of the talks involves public opinion and governmental policy in Western Europe, which demanded such negotiations in connection with the buildup of American nuclear arms on the continent.

Secretary of State Alexander M. Haig Jr.'s planned late January meeting with Soviet Foreign Minister Andrei F. Gromyko will have to be "carefully assessed" in the light of the Polish events, reporters were told. Haig-Gromyko talks require an international climate conducive for such discussion, the senior briefer said, in what seemed to be a hint that they may not be held.

The Haig-Gromyko talks had been expected to set the stage for the reopening of the strategic arms negotiations. So this has been placed in the balance.

Reagan's address last night held the Soviets accountable for the Polish events to a greater degree than his news conference declarations of a week ago today, which was the high water mark until that time of official charges of Soviet responsibility.

It had long been anticipated that a Soviet invasion or Soviet-sponsored crackdown in Poland could produce large-scale changes in the East-West contest that is taking place on a global basis for high stakes. The events of the past 12 days have shaken the chessboard, but so far without clear results.

Reagan's letters and the posture he announced were directed in theory to Poland and the Soviet Union. But the big pieces in motion on the board are those in Western Europe, where governments and publics are shifting positions, and it is clear that the American appeal had that very much in mind.