U.S. Senator John Kerry has canceled some campaign appearances for fellow Democrats, amid a controversy over his remarks about the Iraq war.
Kerry said he does not want to be a distraction from next week's congressional elections.
Earlier Wednesday, Kerry said on U.S. television he is "sorry for a botched joke" he made Monday while speaking to college students in California. He told the students that one can do well if one studies hard, and if not, he said, "you get stuck in Iraq." He said later he was trying to make a joke about President Bush.
Mr. Bush said Kerry's comments are an insult to U.S. troops. A White House spokesman Wednesday repeated the call for an apology.
Kerry ran against Mr. Bush in the 2004 presidential election.
Kerry, a decorated Vietnam Veteran, has said that anyone who believes he would criticize American troops is crazy.
However, some Democrats are distancing themselves from Kerry. Senate candidate Harold Ford has said that no matter what Kerry intended to say, he should apologize to U.S. troops in Iraq.
Democrats are hoping to take control of one or both houses of Congress in the November 7 elections. The war in Iraq is a central issue in many congressional races.
Some information for this report was provided by AFP, AP and Reuters.