Leaders of 10 Protestant denominations moved a step nearer church union last week with their unanimous approval of a concept of ministry for the projected united church.

Despite what was hailed as a major breakthrough for the participants in the Consultation on Church Union, the actual merger of 10 separate and disparate denominations into one united church still remains a distant prospect.

Efforts to bring together American Methodism, Episcopalianism, Presbyterianism and Congregationalism into a single massive church were proposed 20 years ago by the Rev. Dr. Eugene Carson Blake, at that time the head of the United Presbyterian church.

Blake's proposal immediately was endorsed by the late Bishop James Pike, in whose San Francisco cathedral Blake had spoken.

The Consultation on Church Union was organized to attempt to work out the details of the daring proposal.

The document approved last week at the Consultation's Cincinnati meeting envisioned leadership for the proposed united church that would include bishops, "presbyters" or pastors, and deacons.

Not all of the 10 denominations involved in COCU currently have bishops, although all have persons who perform some of the traditional functions of bishops. Among those who do have bishops, there are wide variations in their roles and authority.

The plan that was approved states that the bishops' role would include serving as teachers of the faith, church discipliners, liturgical leaders, administrative leaders and "servants of unity."

It also notes that "the uniting church intends that its bishops should stand in continuity with the historic ministry of bishops as that ministry has been maintained through the ages." This is a reference to the Apostolic succession, in which the authority of the leadership of the church is passed from generation to generation in unbroken succession from Christ's apostles.

The 21-page document approved last week stresses that all members of the church would share a responsibility for all of its activities and that all are in a certain sense obligated to perform its ministries.

At the same time, the church would designate and ordain persons whom it would call "presbyters," for particular tasks such as preaching and teaching, presiding over liturgical and sacramental events, handling pastoral care and administering local congregations.

Deacons -- either employed by the church or not -- would be ordained for special responsibilities in the church. They may serve as leaders of worship, preach when called on, assist in administering the sacraments, and carry out designated administrative tasks.

COCU's member denominations have been asked to study the new document and formally respond to it by the end of 1981.

Earlier documents, already approved by the member churches, deal with membership, faith, worship and unity of the projected new church, which would be called the Church of Christ Uniting.

In 1960, when Blake, who later was to become the general secretary of the World Council of Churches, first made his church unity proposal, it rode on a wave of enthusiasm for Protestant church union.

Only three years earlier, Congregationalists and the Evangelical and Reformed Church had come together to form the United Church of Christ. Two Presbyterian groups had merged into the United Presbyterian Church and United Methodists -- fresh from the reunion that had brought back together Southern and Northern branches that had been torn apart by the Civil War -- had merged with the Evangelical United Brethren.

In the 1960s, the prospect of Protestant church union was overshadowed by the excitement of Protestant-Catholic detente, growing out of the more ecumenical stance of the Roman Catholic Church in its Second Vatican Council.

In the 1970s, the erosion of membership and support of mainline Protestantism worked against church union as the individual denominations faced constant struggles to stay afloat. In addition, the generation of leaders who provided much of the enthusiasm for the church union movement had largely moved out of positions of leadership.

Episcopal Bishop John M. Krumm of Southern Ohio warned COCU delegates last week that "there is a danger that we may be producing papers and issuing statements that the churches are not, by and large, interested at all in reading or hearing, let alone studying and adopting."