Senator Joseph I. Lieberman seized on the terror arrests in Britain today to attack his Democratic rival, Ned Lamont, saying that Mr. Lamont’s goals for ending the war in Iraq would constitute a “victory” for extremists, including those accused of plotting to blow up airliners traveling between Britain and the United States.

“If we just pick up like Ned Lamont wants us to do, get out by a date certain, it will be taken as a tremendous victory by the same people who wanted to blow up these planes in this plot hatched in England,” Mr. Lieberman said at a campaign event at lunchtime in Waterbury, Conn. “It will strengthen them and they will strike again.”

Mr. Lamont, who rode an antiwar message to beat Mr. Lieberman in the Connecticut Democratic primary on Tuesday, has called for a firm deadline to remove front-line American troops from Iraq, and he endorsed a Democratic-sponsored amendment in the Senate to set that deadline for next July. Mr. Lieberman opposed setting a deadline.

In a telephone interview from his vacation home in Maine, Mr. Lamont said he was disappointed with the personal tone Mr. Lieberman’s remarks, and questioned the connection between the Iraq war and the new terrorist plot. He also continued his strategy of trying to link Mr. Lieberman’s views with those of the Bush administration, whose approach the senator has tended to support in the fight against terrorism.