"The message here is that conservative Episcopalians are being pushed out," said spokesman Thomas Peters.
In light of the cathedral's national prominence, Peters called the marriage announcement "an opportunity for people to wake up to what's happening."
"It reminds us that marriage is really an all or nothing deal," he said. "Does America want to retain its marriage tradition or fundamentally give it up?"
Gay weddings will be allowed immediately. But it will likely be six months to a year before the first marriages are performed due to the cathedral's busy schedule and its pre-marital counseling requirement. Generally, only couples affiliated with the cathedral will be eligible. Church leaders had not received any requests for weddings ahead of Wednesday's announcement.
While Hall does not expect any objections within the National Cathedral congregation, he said the change may draw criticism from outside. It may be divisive for some, just as it was to preach against segregation or to push for the ordination of women, Hall said.
The New York-based Episcopal Church is the U.S. body of the 77 million-member Anglican Communion. The House of Bishops voted last year 111-41 to authorize a provisional rite for same-sex unions. Some congregations have left the church over its inclusion of gays and lesbians over the years.
Same-sex marriage is now legal in nine states and the District of Columbia. Legislators in Illinois and Rhode Island are set to take up bills to possibly join them, and the Supreme Court is scheduled to hear cases on gay marriage in March.
The first same-sex wedding performed last month at West Point's Cadet Chapel drew some protests from conservatives. The National Cathedral is even more visible.
Hall, the cathedral dean, said the church has a long history of taking stands on public issues. But he said he sees marriage as a human issue, not a political issue.
"For us to be able to say we embrace same-sex marriage as a tool for faithful people to live their lives as Christian people," he said, "for us to be able to say that at a moment when so many other barriers toward full equality and full inclusion for gay and lesbian people are falling, I think it is an important symbolic moment."