WASHINGTON (CNN) -- Sen. Chuck Hagel, a potential Republican presidential contender and an outspoken critic of the war in Iraq, will announce his "future plans" Monday at a news conference in his home state of Nebraska, aides said.

Hagel's advisers would not explicitly say the two-term senator will announce a bid for the GOP nomination at his Omaha news conference. But he plans to appear at a forum for presidential hopefuls put on by the International Association of Firefighters this week, according to the union. And he told CNN in January that he would make a decision about a presidential run "soon."

Hagel, 60, was a decorated infantry sergeant in Vietnam. He supported the 2002 congressional resolution that authorized the invasion of Iraq the following year, but he has become an increasingly vocal critic of the Bush administration's handling of the war.

He called President Bush's plan to send thousands of additional U.S. troops to Iraq "the most dangerous foreign policy blunder in this country since Vietnam," and joined six other Republicans in February to back a non-binding resolution opposing the troop increase. The measure failed on a procedural vote.