Growing shortages of essential supplies and a hardening confrontation between the government and the church and private business increasingly are spreading dissatisfaction with Sandinista rule in Nicaragua.

The sharpened political atmosphere, combined with strain from a growing war against U.S.-backed counterrevolutionary guerrillas, is pushing the Sandinista leadership toward harder-line policies at odds with its declared goal of political pluralism and a mixed economy, according to diplomats and some Sandinista officials.

Despite the growing tension, however, a visitor seeking to test the atmosphere can find no one eager for a return to the days of the late president Anastasio Somoza and his still-hated National Guard. For this reason, many bitter opponents of the Sandinista government also criticize the U.S.-backed counterrevolutionary movement, which includes many former National Guardsmen, attacking northern Nicaragua.

"That is what the Americans do not seem to understand in using the Somocista National Guard as a spearhead," said Carlos Nunez, a member of the Sandinista National Liberation Front's nine-man directorate that runs the country. "The Somocistas committed such crimes during the war that never will any Nicaraguans accept their return."

But while most Nicaraguans would not want a return of Somoza's supporters, they still complain about the growing lack of everyday necessities such as gasoline, spare parts, toothpaste, toilet paper and a shifting list of food items ranging, according to the day, from cream to cooking oil.

At a small shop in the center of Managua recently, a woman walked in and asked for a local sandwich made with cornmeal tortillas.

"There aren't any today, because there is no cream," the woman at the counter replied wearily.

"Why is there no cream?" asked another customer, a foreigner.

"For the same reason there is no flour, rice, toilet paper and all the rest," replied the shop woman, using an ironic tone at what she seemed to consider a naive question from the gringo.

Two blocks from her shop, a double line of cars wound around a service station, their owners seeking to fill up for the Easter vacation. Gasoline has been rationed here since last summer, with ordinary motorists entitled to 20 gallons' worth of coupons a month. But for the last two weeks, stations have been running out, creating lines reminiscent of those in the United States during the 1973-1974 energy crisis and of Nicaragua during the 1979 revolution that brought the Sandinistas to power.

The scarcity of consumer goods stems from a shortage of hard currency due to insufficient exports and a heavy foreign debt on which the Sandinistas have conscientiously kept up payments.

The hardening Sandinista political line was illustrated in recent weeks by observances marking the centenary of Karl Marx's death, including speeches by Sandinista Commander Victor Tirado that contained some of the most explicit references to Marxism as a goal for Nicaragua in the 3 1/2 years of Sandinista rule.

Underlining the point, a banner has gone up on the fence surrounding the Defense Ministry compound reading, "Marx, the greatest living thinker," and the official Radio Sandino told breakfast-time listeners the other day about how the father of communism was also a devoted father to his children.

In fact, complaints about the Sandinista government often are directed more at its style and rhetoric or abuses by individual officials than at the principle of keeping the revolutionary leadership in power.

A resident of a poor Managua neighborhood complained about pestering by zealots from the Sandinistas' revolutionary block committees, for example, but in the same breath declared support for the revolution and recalled fighting against the National Guard in 1979.

Similarly, residents report that many young Nicaraguans committed to the Sandinista cause have begun to wonder lately about some actions taken by the Sandinista leadership but have not abandoned their enthusiasm for the revolution's principles and goals.

A young government official turned her face away in gloom, for example, when told that the Interior Ministry had barred live broadcast of Archbishop Miguel Obando y Bravo's Easter weekend sermons because the church radio refused to submit them to prior censorship. But within a few moments, she resumed defending the government and blaming economic problems on U.S. pressure against international lending agencies when Managua seeks foreign-exchange loans.

The Sandinista leadership's censorship laws, imposed a year ago under an emergency decree, have been extended to radio broadcasting for several weeks. The dispute over the Holy Week sermons focused public attention on the radio censorship.

Battle lines have hardened noticeably between the government and the church hierarchy since Pope John Paul II's visit here early last month turned into a test of wills. Many Nicaraguans, including Sandinista supporters and officials, were jolted by the sight of the country's leaders shouting "People's power, People's power" while the pontiff tried to say mass.

"People are saying, if they can do that to the pope, the leader of 700 million people around the world, think what they can do to us," said a Catholic activist and opponent of the Sandinistas.

Catholics on both sides of the dispute over church relations with the revolution have concluded that Obando y Bravo emerged from the papal visit with a stronger hand to deal with the government and those among his clergy who support it. As a result, there is a growing expectation among foreign observers and Nicaraguan Catholics that the archbishop plans a showdown with four priests in conspicuous government positions who have been asked to step down.

"To us, the pope has helped us a hell of a lot," said a wealthy business opponent of the government. "That's the best thing that could have happened to us."

His comment reflected a widely held assessment that the church hierarchy increasingly could become the focus of political opposition in this overwhelmingly Catholic country. Under Obando y Bravo's uncompromising leadership, it is considered more able to attract a mass following than the alliance of conservative parties and business groups that constitutes the Sandinistas' tolerated political opposition.

"Obando y Bravo is the most prominent figure of the opposition in Nicaragua," a church activist and Sandinista supporter said.

Whether the sour atmosphere turns into a broader confrontation depends in large measure on the tone of the Sandinista leadership in the months ahead, particularly on the sensitive issues of religious education and the presence of priests in official positions, church sources said.

The nine-man Sandinista directorate's inner workings are largely unknown, even to lower ranking Sandinista officials and diplomats who make a daily job out of studying its ways. This makes predictions difficult, they say.

One Nicaraguan who has dealt with the government frequently said members of the directorate seem to lean in two directions, resulting in personality clashes on certain issues, but agree on the basic course of the revolution.

Financial considerations may end up being more important than ideology in determining which way the nine commanders finally lean, he added.

Using a rough formula, he pointed out that Nicaragua needs about $1 billion a year to service debts and pay import bills, but earns only about $450 million from exports. The rest comes from foreign aid and loans.

As long as international agencies and European countries remain the chief source of the aid and loans, the Nicaraguan leadership, willingly or not, will have to retain a private business sector and a measure of political freedom, he said. If the Soviet Union should step in as the main donor, that need will vanish, he added.

The United States, however, has been pressuring both Western European countries and the multilateral banks to stop aid to Nicaragua.

Undersecretary of Defense Fred C. Ikle said last month in congressional testimony that the Soviet Union has given Nicaragua only $440 million in aid since the Sandinista takeover, compared to $1.6 billion from non-Soviet donors, chiefly European. Reflecting U.S. irritation, Ikle complained that the European governments are misguided in supporting what he described as a trouble-making Sandinista leadership causing turmoil for its neighbors.

But even with the European aid and $150 million a year in help from Venezuela and Mexico for oil, the Nicaraguan source pointed out, the Sandinista government has been unable to raise enough foreign exchange to keep up with its import needs and debt servicing. The count will fall about $200 million short this year, he predicted.

The gap accounts in large measure for the shortages of essential goods on the marketplace, although state takeovers in the distribution system also play a role.

Despite the pinch--and in some ways contributing to it--the Sandinista government so far has kept up payment schedules on its foreign debt, a record not matched by other Latin American countries. To do so, it has had to fight an effort by the Reagan administration seeking to prevent lending agencies and private banks from extending credit to the revolutionary government.