Poland appeared once to be on the brink of major national crisis tonight as workers and authorities hardened their positions while they awaited a Supreme Court ruling Monday that could plunge the nation into a new round of strikes.

In an ominous development, Polish border police today began turning away foreign journalists with valid entry visas, and authorities summoned several Western correspondents to report to the police Monday.

Among those barred entry at Warsaw's airport were American, British, Swedish and Austrian journalists. Austrian Chancellor Bruno Kreisky warned yesterday that Poland's refusal to admit Austrians with valid papers "seriously endangers relations" between the two countries and the Austrian ambassador reportedly was told to protest to the Polish Foreign Ministry.

Throughout the strikes and unrest last summer, foreign journalists with valid visas were permitted to enter the country freely. Some correspondents turned away today said they were told that under a new regulation, only foreign journalist permanently accredited to Poland -- a small minority of those working here -- would be allowed to remain in the country.

Western correspondents said camera crews from the National Broadcasting Co. and the British Broadcasting Corp. were barred at the airport and that a Belgrade-based correspondent of United Press International was being held in the waiting lunge at the airport as U.S. Embassy officials tried to persuade Polish authorities to honor her visa.

Widespread public nervousness about the situation was heightened last night by a film on national television showing recent Soviet-Polish military maneuvers.

A spokesman for the ruling Central Committee of Poland's Communist Party told foreign journalist Friday that Polish troops would not intervene in the country's political struggle but are prepared to keep order in the nation. The Soviet press has been sharply critical of developments here and has repeatedly accused Western interests of meddling in Polish affairs by supporting the workers who last summer won the right to form independent unions.

Thus, 10 weeks after Polish authorities and workers reached an unprecedented compromise that halted the country's most serious labor unrest in a decade, Poland is once again faced with a major crisis.

The Polish Supreme Court is to rule Monday on an appeal by the country's independent trade union federation, Solidarity, demanding that changes written into its charter by a Warsaw court be withdrawn. Unless they are, the union has threatened to begin a new nationwide series of strikes within 48 hours.

The nation tonight was perhaps more tense than during the summer upheaval because communist authorities have indicated this time they will be tougher than they were during the difficult but patient bargaining period last summer.

Poland's crippled economy has hardly recovered from the last round of work stoppages. Meanwhile, the Kremlin and Poland's other communist allies have grown increasingly restive about the concessions made by the Warsaw government at the end of August that allowed the formation -- for the first time in the Soviet Bloc -- of free trade unions and granted to right to strike.

Authorities have accused the new unions of abusing the strike right, which has not been fully defined yet by legislation. They have announced through the foreign press -- which many Poles receive in radio broadcasts and believe more than their own -- that some of the threatened strikes may be declared unlawful.

Few on either the government or union side want another strike, given the high political and economic stakes.

But both sides are firmly entrenched in their positions.

At issue is language avowing the leading role of the Communist Party in the Polish state and other communist principles that were written into Solidarity's charter by the Warsaw court when it registered the union.

Union representatives have pledged to honor these principles, but they object to have them stated explicity in their charter because, they say, such wording will give the new union a political character. Polish authorities argue that the union ought to recognize explicity in its charter the basic principles of the socialist system in which it operates.

The Supreme Court can do one of three things:

Overrule the lower court, withdraw the changes and accept Solidarity's original draft charter.

Affirm the changes.

Return the matter for reconsideration by another panel of judges.

Solidarity's leaders say only the first will avert a strike.

In contrast to the summer strikes, which occurred spontaneously, the work stoppages threatened this week have been extensively planned by Solidarity, which now claims a membership of 6 million to 10 million workers in a nation of 35 million people.

Targeted for strikes are industrial shops, kiosks, gasoline stations and Lot, the national airline. Not striking will be power and heating operations, the phone system, the railways, schools, food stores, restaurants and radio and television -- on the condition that these media do not refuse to broadcast Solidarity's communiques. Buses around Poland will operate according to a schedule to be decided by Solidarity, according to the strike memo.

Voicing determination to counteract the strike, Poland's Communist Part has called a series of regional meetings this weekend to explain the leadership's position to members.

Newspapers have carried speeches of senior party officials warning that a strike at this time would have diastrous effects on the economy, already suffering severe shortages of food and other goods. The party has also stepped up its attack on so-called "antisocialist forces" or dissident groups said to be undermining the Solidarity movement by pushing it too for.

"A lack of mutual trust is behind the problem in Poland now," observed Daniel Passent, a senior editor of the respected Polish weekly Polityka, in a recent talk.

While both the young union and the authorities had begun to work out a tentative understanding, reaching some agreements in recent weeks on media access and wage issues of importance to both sides, the current impasse threatens to reverse the gains so far.

Speaking to a group of journalists Friday, Stefan Bratkowski, president of Poland's jornalistic association, explained the nation's central hope this way: "Everything in this country is striving toward an understanding. One has to hope the two sides will eliminate the greatest impediment, which is stumbling over one's own feet."