Step by step the United States is reasserting its leadership of the Western alliance on the question of Poland.
At this week's special meeting of NATO foreign ministers in Brussels, US Secretary of State Alexander M. Haig Jr. narrowed further the gap between the two sides of the Atlantic and brought the European allies closer to the tougher line that the Reagan administration has adopted from the outset.
But on the morrow of the meeting, Mr.Haig recognized that for allied unity on Poland to be effective, words now need to be matched by deeds.
''We have spoken with one voice about (Poland),'' he said at a news conference in Brussels Jan. 12. ''Yesterday we created a clear and united framework for action. Now we must act.''
What Mr. Haig got the allies to agree to, with Greece demurring, was: that the Soviet Union must bear a major share of the responsibility for the repressive measures that Polish Gen. Wojciech Jaruzelski has clamped on Poland, and that failure to ease repression calls for coordinated sanctions against the Polish regime and the Soviet Union, according to each NATO member's national ability.
Mr. Haig has described this as more than he had expected. But the agreed-upon communique stops short of any commitment by the Europeans to specific measures and short of establishing a time framework or deadline for NATO to move from words to action.
Still the Reagan administration has brought its allies a long way from the relatively passive stance from which they were reluctant to budge the week before Christmas. During that week the State Department's top European specialist, Lawrence Eagleburger, visited major alliance capitals canvassing support for the US policy of sanctions.
Since that week, the Polish issue was raised at: the Brussels meeting Jan. 4 of European Community (EC) foreign ministers, which, of course, the US did not attend; the White House meeting Jan. 5 of President Reagan with West German Chancellor Helmut Schmidt, who had until then been at best a cautious pacesetter for the rest of the European allies on the question of Poland; and finally this week the meeting of the NATO foreign ministers in Brussels.
Each of these deliberations has edged the European allies closer to the US position. That this discomfits both Moscow and Warsaw is proven by the promptness with which both capitals have denounced the NATO communique as unwarranted interference in Polish affairs.
What has contributed to the narrowing of the gap between Washington and its allies?
First, US diplomacy plus European (and particularly West German) recognition in the last resort that the US umbrella is the only and ultimate shield against Soviet expansionism.
And second, the toughening of the stand on Poland of the Roman Catholic Church - from which some European governments have been taking their cue.
Initially both the Pope - himself a Pole - and the primate of Poland, Archbishop Jozef Glemp, had been inclined to give General Jaruzelski the benefit of the doubt as a Polish patriot (and not a Soviet puppet). But a meeting between the archbishop and the general at the end of last week was unproductive. This was reflected in the harshness of the strictures on General Jaruzelski's repressive measures included in Sunday allocutions from the Pope and the primate Jan. 10.
The question now to be answered is: Is General Jaruzelski willing or able (as the NATO communique put it) ''to live up to (his) declared intention to reestablish civil liberties and the process of reform''?
Specifically the NATO ministers called on him to end martial law, to release those arrested, and to restore immediately a dialogue with the Solidarity free trade union movement and the Roman Catholic Church.
General Jaruzelski is unlikely to move in this direction unless his arm is twisted - particularly since the Russians are presumably applying pressure in exactly the opposite direction. The allied threat of sanctions is part of the needed arm-twisting.
The Western allies cannot say so openly, but the arm-twisting could be helped from within Poland - by Polish workers going-slow and refusing to respond to the military regime's call for superhuman efforts to rebuild the country's shattered economy. Whether hungry families and this unusually severe winter will be a brake on any such passive resistance remains to be seen.
As for the Soviet Union, the NATO communique said ''Soviet pressure, direct or indirect, aimed at frustrating'' the Polish people's clear desire for national renewal and reform ''must cease.''
If General Jaruzelski and the Kremlin do not significantly alter course in Poland and the allies transform words into deeds by following through with sanctions, will those sanctions work?
The current issue of the London weekly the Economist answers: ''This is not impossible. If the US, Japan, and the main West European countries would act together, they control between them most of the supply of two things both Russia and Poland want - (a) high-technology machinery and electronics and (b) hard-currency loans and credits.''