NEW ORLEANS — New Orleans Archbishop Gregory Aymond urged delegates attending an ecumenical conference to embrace a longing toward unity.

"God's dream for us is to be a united people, and we must pursue it ... and pledge together to do this," he said.

He made the comments at a prayer service at St. Louis Cathedral that opened the 2010 Centennial Ecumenical Gathering of the National Council of Churches in Christ, which had as its theme "Witnesses of These Things: Ecumenical Engagement in a New Era."

The Nov. 9-11 conference drew more than 400 Catholics, Baptists, Episcopalians, Lutherans, Mennonites, Unitarian Universalists, Orthodox and those of other faiths.

It marked the 100th anniversary of the 1910 World Mission Conference in Edinburgh, Scotland, an event many church historians regard as the beginning of the modern ecumenical movement.

The prayer service included a review of the gathering from its humble beginnings, but along with the history was conveyed the sentiment that while celebration was warranted for the strides toward Christian unity over the past century, the failure to fully receive God's gift of unity remains challenging and lamentable.

In his remarks, Archbishop Aymond told the attendees that the choice of New Orleans for their gathering was appropriate because it is a city of people of faith.

He mentioned how New Orleans had suffered its share of tragedies -- from fires, plagues, hurricanes and the recent oil spill. But it was after Hurricane Katrina that New Orleans had to overcome its fear of strangers, for it was the help of strangers from so many different faiths and ethnicities that "became the hands and hearts of Christ."

The archbishop said people shouldn't wait for a national tragedy to reach out to each other in faith, even though people may initially be strangers. He said he hoped that the centennial observance would heal divisions and offer true unity among Christian religions and get rid of that fear of stranger that is alive even in Christianity.

"We are here together to give thanks to God for the many signs of spiritual revelation and rebirth," he said. "That's what brings us together as Christians."

He rallied believers to cast their needs into the deep, even if it seems foolish to do so. He said Jesus is always with them saying, "Do not be afraid."

"We must have one God, and for that we pray, dialogue and we work," he said. "We welcome and embrace one another no longer as strangers but as brothers and sisters."

Archbishop Aymond suggested that as a unified body "and as a Christian church, we must help our world, our country, our society realize that there are strangers among us, but as Christians we must create a true unity."

He said even as Christians, sometimes we struggle to see the face of Christ in those who are different, the strangers among us. But Christ seeks unity in the diversity.

"We must show the rest of society that it is possible for us to be united," Archbishop Aymond said. "We come here to ask God's strength because more has to be done. ... If we, as a (national) council of churches (of Christ in the U.S.) .... don't take the lead, who will?'"

The gathering offered many opportunities for people of different faiths to explore ways in which they could find common ground.

"We come together as a church and speak with a common voice to a lot of the issues facing our society and world," said Father Robert Nemkovich Jr., a delegate from Fall River, Mass., representing the Polish National Catholic Church.

Those participating explored a diversity of issues facing the church and world today including social justice, interfaith issues, race and ethnicity, the need to engage young adults, and Muslim and Jewish relationships.

Speakers and preachers ran the gamut from the Rev. Lois M. Wilson of the United Church of Canada; the Rev. Olav Fykse Tveit, general secretary of the World Council of Churches; Rabbi Steve Gutow, president of the Jewish Council for Public Affairs; Sayyid Syeed, national director of the Office for Interfaith and Community Alliances for the Islamic Society of North America; and Bishop Vashti Murphy McKenzie, of the African Methodist Episcopal Church. Greek Orthodox Archbishop Demetrios also led a Bible study.

Many sessions were small group discussions called "cafe conversations" led by a facilitator concerning the future of ecumenism. Discussions centered on a Christian understanding of unity in the age of radical diversity, mission in an age of interfaith relations, creation in an age of environment crisis, war in an age of terrorism and economy in an age of growing inequality.

The gathering also offered a work project through Project Homecoming to help rebuild New Orleans and served as the annual meeting of the U.S. Conference for the World Council of Churches.

The hope is "we can do something together whether as Christians or believers," Father Anthony Mikovsky of Scranton, Pa., said. "It's part of discernment, to see what we can do together."