Ahead of the Republican convention the party's leader is calling for unity, even as some delegates plot a challenge to Donald Trump.

FOX News Radio's Jared Halpern has more from Cleveland:

RNC Chairman Reince Preibus tells delegates and party officials here they must stand united.

(Chairman Preibus) Now is the time to stop Hillary Clinton and elect Donald Trump President of the United States. 

Republican lawyers insist the rules, as written, require delegates to follow the results of their states' primaries and caucuses results unless the convention's rules committee makes changes.

That 112 member panel meets here Thursday a last stand for some anti-Trump delegates to try to recommend a change and let each vote his or her conscience, a move that ultimately would need a majority vote by the full slate of Republican Delegates next week.

In Cleveland, Jared Halpern, Fox News

Follow FOX's Jared Halpern on Twitter: @jaredhalpern