WASHINGTON, Jan. 2 (RNS)--The stately Washington National Cathedral will be the site of a colorful celebration of "full communion" between theEvangelical Lutheran Church in America and the Episcopal Church at 10:30a.m. Saturday--the Feast of the Epiphany--as the two churchesjoin to celebrate a new relationship for the 21st century.

Hundreds are expected at the cathedral to celebrate theimplementation of the "Called to Common Mission" agreement, which willallow the two churches--with a combined membership of 7.7 million--toswap clergy and share in common mission projects.

The accord, ratified by Lutherans in 1999 and the Episcopalians in2000, stops far short of an outright merger but allows the twodenominations from divergent historical backgrounds to weave theirministries together.

"There is no more fitting way to launch our shared mission andministry than by hearing Christ's promise and welcoming his presence inthis eucharistic service," said Lutheran Presiding Bishop H. GeorgeAnderson, who will lead the communion portion of the service.

The Rt. Rev. Frank T. Griswold, presiding bishop of the EpiscopalChurch, will deliver the sermon and preside over the renewal ofbaptismal vows of the hundreds of guests and dignitaries.

The accord has taken 40 years of dialogue to resolve and overcomesharp disagreement. The first draft was floated by the Episcopalians in1991 and ratified in 1997. Lutherans, however, failed by just six votesto pass the measure the same year. The final draft was passed byLutherans in 1999, and then by the Episcopalians last July.

The agreement will allow both churches to share precious resourcesin rural and urban areas. The future of the deal is best seen in placeslike Bridgton, Maine, where the Rev. David Snyder, a Lutheran, serves aspastor to St. Peter Episcopal Church, a 45-member parish without afull-time pastor.

The Rev. Daniel Martensen, the Lutherans' director of ecumenicalaffairs, said the agreement bridges an "ecumenical chasm" between thetwo churches.

"The bridge has been under construction for nearly four decades; itspans not only two U.S. communions, but also continents," Martensensaid in a statement produced by both churches.

Still, the agreement is not without its critics. A large faction inthe Lutheran church opposes the agreement because of new ordinationstandards agreed to by Lutheran negotiators.

Historically, Lutheran pastors could be ordained by either otherpastors or the local bishop; Episcopalians insist on ordination only bya bishop who is a member of the "historic episcopate" stretching backto the early church.

Some Lutherans, particularly in the upper Midwest, say requiringordination by bishops runs against Lutheran identity. They want theirpastors--and not just bishops--to continue to ordain new pastors, butsuch pastors would not be able to serve in Episcopal parishes. When theLutherans meet in Indianapolis in August, church leaders hope to draft afinal compromise.

The. Rev. Mark Chavez, executive director of the Word Alone Network,which opposes the agreement, called the Washington ceremony a "sadoccasion."

"It's celebrating a false unity," Chavez said. "The unity is notbased on truth, and there is no unity in the historic episcopate. Ithasn't united the [Episcopal Church] with the Catholic Church or theOrthodox Church, so why will it bring unity with the Lutherans?"

The ceremony hopes to combine the best talent from both churches,with the Cathedral Choir singing alongside the acclaimed St. OlafCollege Choir, a Lutheran-affiliated school. Representatives of theWorldwide Anglican Communion--of which the Episcopal Church is the U.S.branch--will attend the ceremony, along with officials from theLutheran World Federation.