The St. Patrick’s Day parade in Boston is easing its two-decade ban on gay organizations under a tentative deal to allow them to march in an event that once went to the Supreme Court to keep gays out, a marriage equality group said Saturday.

MassEquality Executive Director Kara Coredini said a group of gay military veterans can march under its banner as part of a tentative deal with parade organizers brokered by Boston Mayor Martin Walsh.

Marchers from the gay-rights group would not, however, be allowed to wear clothing or hold signs that refer to sexual orientation, Coredini said.

Negotiators will work out final details in the coming week, she said.

“But we are encouraged this conversation is happening. That is a significant step forward,” Coredini said

Although there are still particulars to hammer out, Coredini said the development is a big deal for members of the lesbian, gay, bisexual and transgender community.

“The LGBT community faces many challenges more significant than this parade, but the parade has been historically been the symbol of those challenges that we face,” Coredini said. “It’s been 20 years since openly LGBT people have been able to march in this parade.”

The Boston parade, sponsored by the South Boston Allied War Veterans Council, has had a long and torturous history on the question of whether gay groups can march.

State courts forced the sponsors to allow the Irish-American Gay, Lesbian and Bisexual Group of Boston to march in the parade in 1992 and 1993. In 1994, the sponsors canceled the parade rather than allow the group to participate.

In 1995, the sponsors made participation by invitation only and said the parade would commemorate the role of traditional families in Irish history. Several months later, the U.S. Supreme Court ruled unanimously that Massachusetts courts had previously violated the parade sponsors’ First Amendment rights when they forced them to allow the gay group to participate.

Walsh, the son of Irish immigrants, had threatened to boycott the city’s annual parade unless gay groups are allowed to march. He said the agreement is a breakthrough.

Walsh’s predecessor, Mayor Tom Menino, boycotted the parade after the Supreme Court ruling.