PORTO ALEGRE, Brazil — In promoting Christian unity, the World Council of Churches has taken its work seriously: Each of its meetings has grown bigger and more ambitious over the past six decades.

But now even some of the most ardent backers of the WCC's mission are wondering if smaller may be better.

During the WCC's latest global assembly — bringing together 4,000 envoys from more than 350 churches — delegates challenged the group to look hard at whether such parliament-style mega-meetings are still relevant at a time when Christianity is being rapidly reordered around the world.

In the West, mainline Protestant churches face graying congregations and declining influence. Some denominations, most notably Anglicans, also are in danger of splintering over disputes on gay clergy and same-sex blessings. Pentecostal and evangelical movements, meanwhile, keep steamrolling through Africa, Latin America and elsewhere — but accounted for less than 2 percent of participants at the WCC gathering, which began last week and ended Thursday.

"The ecumenism of structures, the ecumenism of papers and documents and speeches has reached its limits," said Norberto Saracco, a Pentecostal pastor and theologian from Argentina. "We cannot continue in this way."

It was more than just grumbling from groups outside the WCC, whose core membership includes mainline Protestants, Anglicans and Orthodox churches. (The Roman Catholic Church is not a member, but cooperates closely.)

The keynote address of the conference repeatedly raised the idea that Christian churches need to find clearer ways to connect and cooperate beyond simply sharing the stage at meetings and issuing joint communiques.

Catholicos Aram I, the spiritual head of the Armenian Apostolic Church, sounded at times like a CEO, saying the WCC must become more "efficient and credible" and reverse an "in-house mood of restlessness," with the group's income declining by about 30 percent since 1999.

Aram, the moderator of the assembly, urged for more outreach to the evangelical powerhouses and stressed that the WCC members must learn how to engage more with youth or risk becoming spiritual dinosaurs.

"The ecumenical movement, for some, is getting old. For others, it has already become obsolete," he told the conference last week. "Institutional ecumenism has been preoccupied with its own problems and, therefore, lost touch with the issues facing the churches."

The modern map of the Christian world has little in common with the Euro-centric model at the WCC's founding congress in 1948. The Christian centers of gravity now reside in the countries where European missionaries once brought the faith.

"Mainstream Christianity is aging and falling in number," Aram said. "Christianity is re-emerging with new faces and forms ... that have dramatically changed the Christian panorama."

But it's not clear what that means for the WCC and its tradition of big-tent meetings. The only consensus is that it cannot afford to freeze out the Pentecostal, evangelical and related churches, which some experts predict could account for more than a third of the world's 2.2 billion Christians in less than 20 years.

The handful of Pentecostal and evangelical guests at the Brazil conference expressed a desire for closer contact with the WCC, but gave no clues on how it could happen. There is still deep resistance across the movements for such pan-Christian alliances.

Many pastors worry that the WCC will try to rein in their spontaneous style of worship and their plans for expansion, which are often bankrolled by what's called "the Gospel of prosperity" which says God smiles on those who help the church.

But the mainline churches seem to have little choice but to make room. Some WCC veterans say the future could include fewer academic speeches and large conventions. Instead, they foresee more attempts at joint worship and social programs — especially those aimed at young people in the West.

"Many people, especially youth, have lost hope and confidence in 'official' deliberations for unity," said the Rev. Jabob Kurien, vice principal at the Malankara Orthodox Syrian seminary in India. "They have been seeking alternative channels of Christian unity."

It could be as simple as flipping the equation, some say. Phase out the big congresses of like-minded delegates and concentrate on those who have drifted away from the churches. That means less academic language and more plain speaking, said Jantine Heuvelink, a delegate from the Protestant Church in the Netherlands.

"To make myself understood is make Christianity understandable," Heuvelink said. "Grass-roots people speak best for the church."