Following three days of tempestuous debate, U.S. Lutheran leaders yesterday passed a historic union with Episcopalians, enabling the two churches to recognize each other's members and sacraments and making their clergy essentially interchangeable.

Sixty-nine percent of the 1,033 voting bishops -- slightly more than the required two-thirds -- consented to the union, after intense lobbying on both sides at the biennial Lutheran convention in Denver. The agreement advances the widely held Christian goal of breaking down barriers between different denominations and uniting in a common church.

The union will take effect following approval by the Episcopalians, who are scheduled to meet next July and who have already approved an earlier draft of the document.

Supporters of the union were elated for reasons both idealistic and practical: in part because Christians took a big step toward fulfilling Jesus's vision in John 17 that his followers "may be one," and in part because two mainstream Protestant denominations that have watched their numbers dwindle over the last 30 years are now, while remaining distinct, united into a fellowship 8 million strong.

"I am quite pleased," said Bishop Theodore Schneider of the Metropolitan Washington D.C. Synod of the Evangelical Lutheran Church in America. "This was a vote on our soul, a vote defining what we're about as we move into the 21st century."

"In a world that's increasingly secular and self-centered," Schneider continued, "oneness becomes a proof of the authenticity of the gospel."

The agreement, a version of which failed to pass two years ago, brings together two very different American religious traditions: Lutherans, headquartered in Chicago, trace their roots to hardscrabble Norwegian immigrant farmers in the upper Midwest. Episcopalians, based in New York, are an independent province of the Anglican Church and are more closely associated with the Northeastern elite.

The debate was marked by an unusual amount of open politicking and scheming, as each side bombarded the bishops with mailings and calls in the months leading up to the agreement, and set up competing hospitality centers at a downtown Denver hotel.

By signing the document, "Called to Common Mission," the bishops in the Evangelical Lutheran Church in America, the sixth-largest Christian church in the country with 5.2 million members, conceded the main sticking point of the debate: Lutheran clergy will have to give up their relatively informal ordination process and follow what is known as the "historic episcopate." In the future, all new clergy must be ordained by a bishop, and each new bishop must be ordained by three bishops in a line believed to extend back to Christ's apostles.

For opponents, this represents the kind of bow to power and rigid hierarchy Martin Luther saw as a temptation to corruption. Many pointed out that the new agreement contained the word "bishop" 40 times, while the word "mission" appeared fewer than 15.

Many opponents of the union came from old Lutheran strongholds such as Minnesota and the Dakotas, where the memory of a controlling Norwegian state church still festers. Used to scattered, loosely controlled congregations, they bristled at the idea of giving bishops more power.

Among urban, coastal Lutherans, this new role for bishops was less of a concern. At a meeting in June, more than 90 percent of Lutherans in the D.C. synod voted to approve the document, according to Schneider. In anticipation of the document's passing, Schneider has already been holding joint clergy training with Episcopalians and planning other shared missions.

Schneider hailed the agreement as a landmark for ecumenism, the crusade to unite all Christian denominations by the next century. Conceived as a utopian vision in the mid-'50s, ecumenism has since been embraced by most mainstream Christian leaders in America and elsewhere, including Pope John Paul II, who plans to sign a less sweeping but equally historic document linking Catholics with Lutherans on Reformation Day in October.

Yesterday's agreement makes Lutherans a bridge between divergent traditions of the Reformation churches that broke away from Catholicism in the 16th century, with the more traditional, hierarchical Episcopalians on one end, and the more progressive United Church of Christ -- with whom the Lutherans have a similar agreement -- at the other.

Ecumenism has taken on more urgency in the last few years as mainstream Protestant denominations realize they are fast losing members to the more vibrant evangelical churches. Since 1965, Episcopalians have lost about 20 percent of their members, and Lutherans about 6 percent, while some denominations, such as United Church of Christ, have lost almost half.

By banding together, many church leaders believe they can regain some of their vitality.

But others are dubious. "Ecumenism is self-defeating," said Randall Balmer, professor of American religion at Columbia University and an Episcopalian who opposed the agreement with the Lutherans. "For better or for worse, the most successful religious movements have been exclusive. By dissolving any historical, doctrinal difference, they're creating a mainline Protestant mush which means nothing."