Topeka ? Supporters and opponents of adding a ban on same-sex marriage to the Kansas Constitution expect hundreds of people to converge Monday on the Statehouse for rival rallies, as legislators open their annual session.

Some clergy, disappointed by the Legislature’s refusal last year to adopt a proposed amendment, want lawmakers to move quickly enough this year to put a proposal on the April ballot for municipal and school board elections.

Pastors supporting the effort are planning a rally for 1:30 p.m. in the second-floor rotunda. About 250 ministers have committed to participate, the Rev. Terry Fox, senior pastor of Wichita’s Immanuel Baptist Church, said Thursday.

Also set for 1:30 p.m. is a rally outside on the Statehouse’s south side, organized by opponents of the proposed ban. Some also support abortion rights or are concerned about preserving the separation of church and state, said Tiffany Muller, a Topeka City Council member involved in the event. Muller said she expected about 400 people to participate.

Kansas already has a law against same-sex marriage, but advocates see an amendment as a way to ward off a court challenge.

Both legislative chambers must adopt a proposed amendment by two-thirds majorities to place it on the ballot, with approval by a simple majority of voters needed to add it to the constitution.

Fox and other clergy support a proposal to not only ban same-sex marriage but also prevent civil unions or other forms of legal recognition for gay relationships. Last year, the Senate approved such a proposal. While a majority of House members supported the measure, it fell short of the two-thirds margin.