President Bush has challenged critics of his new Iraq strategy to come up with their own plan to bring the violence there under control.
In his weekly radio address, Mr. Bush said opposing everything while proposing nothing is irresponsible.
But in his party's response, Representative Tim Walz said Democrats must ask tough questions to make sure the president is not escalating the Iraq problem. Most Democrats and some Republicans say sending more troops to Iraq will only make a bad situation worse.
Opinion polls also indicate many Americans do not favor more troops.
But the president says Iraqis need the help of the United States to execute an "aggressive" plan to secure Baghdad and troubled Anbar province - where the worst sectarian violence is occurring. He said both goals require additional US troops.