Baptist minister Buni Cocar insists he never meant to challenge Romania's Communist government. He never wanted to break the law, he says, and he certainly never expected that in the end he would be cornered by bureaucrats, bulldozers and police in the ruins of an old back-street chapel.

All he ever wanted, Cocar says, was to rebuild his Holy Trinity Church.

"We were growing, and there was no room for all the people anymore," Cocar explained one recent morning, pacing restlessly atop the rusting tin roofing of Holy Trinity, a one-room concrete structure tucked between small family homes in northeast Bucharest.

"We wanted to do something nice, to make a proper building. We didn't want to make a revolution. We just tried to put up a new roof."

Such a project might seem common in a capital where thousands of old buildings and whole neighborhoods are being flattened and reconstructed. But in austere, ruthlessly regimented Romania, even the quiet reshaping of a chapel on a disheveled back street is a glaring exception to state controls over religion and its practice.

As a result, helmeted militia and demolition crews arrived at Holy Trinity one Saturday morning this summer, tore down its new roof and annex, and prohibited its volunteer builders from putting up so much as a canvas to cover the gaping hole left in its side wall.

Cocar, the church's pastor, was heavily fined and ordered to leave Bucharest, and the church's two deacons were fired from their state jobs after being detained and beaten by police.

Now, Cocar and his congregation find themselves in a test of wills with government authorities. They have resolved to remain in their church through the winter, and the 33-year-old minister, who left Bucharest briefly, has defiantly returned. "We'll get by somehow," Cocar said. "But we won't abandon the church. These people here have nothing more to lose."

The standoff has little political significance in a country whose Communist president, Nicolae Ceausescu, has consolidated a formidable structure of personal power and eliminated virtually all signs of dissent. Yet Cocar's crusade illustrates how some Romanian churches have become the homes of independent-minded communities willing to challenge the government aggressively on issues of expansion, proselytism and control over religious organizations.

"The churches are becoming more appealing, and the more aggressive they are, the more people they attract," a western diplomat here said. "It is a reaction to the stagnant and hopeless situation the regime has brought people to."

Romania has the largest church attendance among Eastern European countries after Poland, and many church leaders believe membership has been growing in recent years. While the Orthodox Church, followed by an estimated 70 percent of all Romanians, generally avoids all confrontation with the government, many of the country's 13 other recognized denominations show more independence despite state controls over their finances and activities.

The Baptists, whose growing numbers have been variously estimated between 100,000 and 300,000, have in recent years sought to expand churches or build new ones all over the country, often in defiance of official restrictions.

Authorities have often responded toughly. Several churches, like Holy Trinity, have suffered from official demolitions, and international human rights groups have reported a number of instances of persecution of Baptist activists.

At the same time, western diplomats here say, government repression of church activities has often been carefully restrained, perhaps in deference to the interest taken in Romanian Protestant churches by fundamentalist groups in the United States.

"It's a game that's played here," a diplomat well acquainted with church activities said. "The churches try and get away with things, and the authorities sometimes let them. The times when the authorities react more violently are those when they perceive a direct provocation."

In Cocar's case, the provocation seemed to arise from the very energy of a young minister intent on multiplying the numbers of his followers and impatient with formal restrictions. The son of a pastor from the interior town of Medias, Cocar finished divinity school in Bucharest in 1978, then was licensed by authorities to live and work in the oil-mining town of Petrosani.

Cocar took over a Baptist church there with 70 members and more than doubled the size of its congregation in a year-long campaign. Then, in 1980, he decided to return to Bucharest and revive the Holy Trinity Church, which had stagnated for years while its congregation sank from 150 to 20.

Authorities refused to grant the ambitious young preacher permission to live in the capital and stripped him of his religious license. But the determined Cocar stayed anyway, making his own contract with Holy Trinity's remaining members.

For several years, his presence in the poor, aged neighborhood of Giulesti was tolerated. Attendance at Holy Trinity grew until up to 500 people were crowded into its chapel and tiny side yard for thrice-weekly services.

Even before Cocar's arrival, Holy Trinity had been denied permission to expand its chapel or even to repair structural damage from a 1977 earthquake. But Cocar quietly led volunteers in building expansions that extended the chapel by a third and widened it across the yard.

Finally, Cocar and church leaders decided last February to launch a definitive renovation. Using plans drawn up by a friendly architect and materials bought from state construction companies, 100 church volunteers worked in teams with 20 moonlighting specialists to put up a new, arching roof 35 feet high at its peak -- the beginning of a local landmark.

The project was already well into its fifth month and new interior walls for the church were being prepared when Bucharest's mayor called in Cocar and told him he had gone too far. Shortly afterward, the demolition crews arrived and went to work despite the occupation of the chapel by several dozen members of Holy Trinity.

Fined more than 30,000 Romanian lei, or about $2,000, for offenses ranging from living in Bucharest to violating zoning codes, Cocar was forced back to Petrosani. But he came back to the city in September and shortly afterward a large tent appeared alongside the damaged chapel, covering the partially disassembled side wall.

Authorities soon appeared and ordered the tent removed. But Cocar has remained in Bucharest and doggedly gone on planning for the coming winter.

"We'll buy some overcoats," Cocar said. "Maybe we'll find another canvas to cover the side. The old ladies will have to stay home and wait for spring. But the majority will stay here, whatever happens."