WASHINGTON (Reuters) - U.S. Republican presidential candidates Chris Christie and Rand Paul will be in the prime-time lineup for the party's next presidential debate, CNN said on Sunday.

Donald Trump will hold center stage as the party front-runner on the main stage on Tuesday night in Las Vegas, CNN said, flanked by retired neurosurgeon Ben Carson and Ted Cruz, who took the lead in an Iowa opinion poll on Saturday.

Christie, following a surge in support in the early voting state of New Hampshire, will return to the prime-time debate after being bumped off it for a Fox Business debate last month, CNN said.

Paul kept his spot thanks to a Fox News Iowa poll released Sunday that showed him strong enough in that state, according to CNN.Others on the main stage include Senator Marco Rubio, former Florida Governor Jeb Bush, businesswoman Carly Fiorina and Ohio Governor John Kasich, the network said.

Rand Paul, dipping in the latest opinion polls, had risked being placed with the lower-polling contenders in the large Republican field, which hold an earlier debate.

Those include Mike Huckabee, the former Arkansas governor, former U.S. Senator Rick Santorum, former New York Governor George Pataki and U.S. Senator Lindsey Graham.

(Reporting by Doina Chiacu; editing by Andrew Roche)