WASHINGTON (AP) - Republican Sam Brownback said Wednesday he will drop out of the race for president if he finishes lower than fourth place in the Iowa caucuses.

The Kansas senator previously had said he would consider ending his campaign for the GOP nomination if he could not finish in the top four.

Brownback made the comments while fielding questions in a live Internet discussion on washingtonpost.com.

In response to a questioner who asked whether Brownback planned to end his bid if he places outside the top four contenders, Brownback said, "That is correct. I need to finish in that group to move on forward."

A poll conducted for The Des Moines Register earlier this month shows Brownback in seventh place and drawing support from just 2 percent of Republicans surveyed.

The poll shows former Massachusetts Gov. Mitt Romney leading the race with 29 percent, followed by former Tennessee Sen. Fred Thompson, Arkansas Gov. Mike Huckabee and former New York City Mayor Rudy Giuliani.

Brownback said he remains hopeful that he can break into the top tier of candidates before the January caucuses.

"The Republican side of the field is unsettled," Brownback said. "It is not determined who will be our nominee - far from it."

Brownback has spent more than a year courting Iowa's religious conservatives with his strong anti-abortion message and a pledge to "rebuild the family and renew the culture." Recently, he has focused more attention on his foreign policy credentials.

This Friday, Brownback will make an unusual campaign appearance in Iowa with Delaware Sen. Joe Biden, a long-shot Democratic presidential candidate, to promote their plan to divide Iraq up into three semiautonomous regions - for the Kurds, Sunni and Shiite groups - with a decentralized federal government.

The measure passed the Senate last month on a 75-23 vote, and Iraqi President Jalal Talabani endorsed the proposal last week.