Sen. Chuck Hagel, a Republican critic of the White House’s handling of post-war efforts in Iraq, is scheduled to speak at a conference co-hosted by two progressive organizations later this month, causing uneasiness among some GOP leaders about the Nebraskan’s upcoming speech.

The event, being billed as a conference “on new directions for U.S. national security,” touts Hagel, retired Gen. Wesley Clark and Zbigniew Brzezinski as its “featured speakers.” Clark is seeking the 2004 Democratic presidential nomination, and Brzezinski served as President Jimmy Carter’s national security adviser.

Several Republicans said they are concerned the outspoken Nebraska Senator would use the forum to offer a further critique of the administration’s reconstruction plans for Iraq.

Last month, Hagel told CBS’ “The Early Show” that the White House did a “miserable job of planning for a post-Saddam Iraq” and criticized administration officials for treating “most of the Congress like a nuisance when we asked questions.”

Eyeing next year’s elections and President Bush’s recent slippage in the national polls, a Senate Republican leader said it is imperative that Republican Members refrain from criticizing Bush for his handling of Iraq. “I think we are fooling ourselves if we think we are not in the political season, and you know Democrats are attempting to undermine the president’s ability to lead,” said the Senator, who spoke on the condition of anonymity.

“All of us have got to be careful in this political season to not send messages that undermine the ability of the United States to lead in Iraq.”

Hagel said he is not sure what he is going to talk about and downplayed his anticipated participation at the conference.

“I speak to a lot of groups,” Hagel said Wednesday. “Quite honestly, I probably speak three times a day to groups, to all kinds of groups by the way.

“There is no point in speaking to your own kind,” he said.

The event is being sponsored by the Center for American Progress, The American Prospect and the Century Foundation. CAP is a new progressive think tank founded by John Podesta, President Bill Clinton’s chief of staff, and the Prospect is a magazine that promotes liberal viewpoints.

Hagel dismissed an advisory distributed by the event’s organizers that hypes the conference as “a coming together of experts and practitioners who share grave concerns about the wisdom of the current course of America’s foreign policy.”

“Every organization can say what they want,” said Hagel, who, when asked, would not offer his assessment of Bush’s handling of foreign policy matters.

“Listen, they got their hands full and we have a lot of work to do this week, and we are going to help them get through it,” he said.

But sources close to the Senate Republican leadership and the administration said there is “concern” among senior officials that Hagel is angling to fill Sen. John McCain’s role as a conservative contrarian when the Arizona Republican leaves the Senate.

“As far as the administration goes, he is a thorn in their side on many issues of importance,” said a source close to senior White House officials.

“While for the most part he votes with the Republican caucus, there is a sense that he is more McCain than McConnell,” the source said, referring to Senate Majority Whip Mitch McConnell (R-Ky.).

Bob Boorstin, CAP’s senior vice president for national security, said the group has not spoken to Hagel about his speech and is “just very happy he has agreed to participate because he is such an articulate voice on these issues.”

“This is his speech to give,” said Boorstin, who noted that Rep. Jim Leach (R-Iowa) is one of several Republicans who would also actively participate in or attend the conference. A spokesman for Leach said the Iowa Republican is a member of the nonpartisan The Century Fund.

A senior Senate Republican aide said there is “no question” GOP leaders would be closely monitoring Hagel’s remarks but added, “You have to withhold judgment until you hear what the man has to say.”