WASHINGTON (CNN) -- Presidential candidate and Delaware Sen. Joe Biden said Thursday he is working on legislation to "repeal" the 2003 congressional authority that allowed President Bush to take military action against Iraq.

"We gave the president that power to destroy Iraq's weapons of mass destruction and, if necessary, to depose Saddam Hussein," Biden said in prepared remarks of speech to the Brookings institution, a Washington think-tank. "The WMD were not there. Saddam Hussein is no longer there. The 2002 authorization is no longer relevant to the situation in Iraq."

Biden said he would work to offer new legislation that redefines the U.S. mission in Iraq, making it much "narrower."

"Congress should make clear what the mission of our troops is: to responsibly draw down, while continuing to combat terrorists, train Iraqis and respond to emergencies," Biden said. "We should make equally clear what their mission is not: to stay in Iraq indefinitely and get mired in a savage civil war."

Biden also reiterated his plan to divide Iraq into its three political factions in a way that, he said, divides "power peacefully and offers us a chance to leave with our interests intact."

"We have to convince the major powers and Iraq's neighbors that a federal Iraq is the best possible outcome for them, too, and to put their weight and influence behind it," Biden said. "Then, together, we have to bring in the Sunnis and convince the Shiites and Kurds to make concessions."

Biden, chairman of the Senate Foreign Relations Committee, announced he was seeking the Democratic presidential nomination late last month. He is slated to head to the early-voting state of Iowa this weekend, though his plans could change after Senate Majority Leader Harry Reid scheduled a vote Saturday on the House resolution condemning the troop increase in Iraq.