NEW YORK (AP) _ Democrats, in a move to dramatize broad support for the cause of abortion rights, are taking the unusual step of featuring a Republican speaker at their national convention today.

''A pro-choice Republican woman is going to speak'' as part of a presentation on abortion rights, said a Democrat involved in scheduling.

The Democrat, who spoke on condition of anonymity, refused to name the speaker but said she was not a prominent Republican.

''We think it's representative of Republican voters who will be crossing over to vote for the pro-choice ticket,'' the Democrat said. ''The idea is that this represents a trend that's going to occur.''

Pennsylvania Gov. Bob Casey, a Democrat who is anti-abortion, has been trying this week to get a few minutes to address the convention on his views. He complained Monday that the party had ''imposed a gag rule.''

Casey says that what he calls the Democrats' ''abortion-on-demand'' position is morally wrong and politically costly. A party spokesman indicated Monday he will not be given podium time to air that view.

Casey did testify last spring at a Democratic platform hearing in Cleveland.

''Bob Casey has had ample opportunity'' to express his views, the Democratic planner said. ''The sense is that Casey in terms of this issue is not representative of his delegation or the party.''

Republicans who favor abortion rights are trying to get their party to change its ironclad opposition. But it is unclear whether they will succeed in getting platform changes next month at the GOP convention in Houston.