FALLS CHURCH, Va. — They are two of the biggest churches in the Episcopal Diocese of Virginia, with roots stretching back to Colonial times. One even had George Washington as a lay leader. But next week, The Falls Church and Truro Church will vote whether to break their centuries-old ties to the national denomination as its fight over the Bible and sexuality intensifies.

Parishioners who support a split say they can no longer abide what they see as moral backsliding by the Episcopal national leadership, marked most starkly by the 2003 consecration of the first openly gay bishop, V. Gene Robinson of New Hampshire.

The two Virginia churches hope to align themselves with Anglican Archbishop Peter Akinola of Nigeria, among the fiercest critics of Robinson's election. The archbishop is seeking to create a U.S. alliance of disaffected parishes as a rival to the Episcopal Church.

The Episcopal Church is the U.S. branch of the 77 million-member world Anglican Communion, which is struggling to stay unified despite deep divisions over whether gays should be ordained.

Most overseas Anglicans believe gay relationships violate Scripture, but conservatives are a minority within the 2.2 million-member Episcopal Church. Still, the protests by traditionalist Episcopalians have had an impact. Last week, the Diocese of San Joaquin, in Fresno, Calif., took what its leaders called a first step toward a formal break with the national church.

The potential split by the two Virginia churches comes after three years of effort by local Bishop Peter James Lee to keep conservatives in the fold. Lee, who voted to confirm Robinson, has earned praise for his outreach even from those who opposed his vote.

Now, the Virginia bishop is warning that any move by the prominent Virginia parishes to leave could prompt nasty lawsuits over who owns the historic properties.

Lee said he respects the crisis of conscience some feel, but he said there is no recognized way for a church to leave the diocese as a group and take their property with them.

"We live in a free country, and individuals are free to walk away," Lee said.

Several small Virginia churches have already broken with the denomination, but none are of the size or the historic importance of Truro, located in Fairfax, and The Falls Church.

The two congregations' roots stretch back to before the denomination formed in the United States. The city of Falls Church took its name from the Episcopal parish when the city incorporated in 1948. On an average Sunday, nearly 1,300 people worship in Truro Church, and more than 1,900 attend services at The Falls Church. Each church claims more than 2,400 members.

The vestries, or boards of directors, of both parishes voted last month to recommend a split. Parishioners, starting tomorrow, will vote through Dec. 16 whether they should leave. A super-majority of 70 percent of those who cast ballots is required to approve a break.

"The vast majority of members are very concerned about the direction of this church, and it's very likely that the upcoming vote will reflect that," said the Rev. Rick Wright, associate rector at The Falls Church.

The churches' leaders believe Virginia law will be on their side in a property battle. They say a state statute dating back to the Civil War favors congregations over denominations in such property disputes, provided that a majority of all church members vote to leave.

The diocese disputes this. Lee said he has been advised by canon lawyers that the hierarchical structure of the Episcopal Church favors the diocese over the parish and that a civil court would be violating the denomination's religious freedom if it were to intervene in favor of the two churches.

"I really want to avoid litigation if at all possible," said Lee, who raised the possibility of some type of settlement involving property sharing or a buyout. "But we do operate under a system of order and discipline, and I have an obligation to bring to the attention of those congregations the potential repercussions of their actions."

Valerie Munson, a Philadelphia-based lawyer who specializes in religion and law, said civil courts consider a variety of competing principles when they wade into such disputes.

"People on both sides of the issue would like to state it in black-and-white terms, but it's not," Munson said. "If courts judge these cases following neutral principles of law rather than politics, they are going to be very difficult cases to decide."

Lee is continuing to press for discussions even as the churches prepare to vote.

"We are in the hope business," Lee said. "We never give up hope."