BELGRADE, Mont. — Republican Senator Burns, whose recent comments have stirred debate, has said America is up against a faceless enemy of terrorists who “drive taxicabs in the daytime and kill at night.”

During a fund-raiser Wednesday with first lady Laura Bush, the three-term Montana senator talked about terrorism, tax cuts, and the money that he has brought to his state. Mr. Burns is one of the more vulnerable Senate incumbents, facing a tough challenge from a Democrat, Jon Tester.

He has drawn criticism in recent weeks for calling his house painter a “nice little Guatemalan man” during a June speech. Mr. Burns, whose re-election campaign is pressing for tighter immigration controls, also suggested that the man might be an illegal immigrant. The campaign later said the man is a legally documented worker.

Mr. Burns, 71, also had to apologize after confronting members of a firefighting team at the Billings airport and telling them that they had done a “piss-poor job,” according to a state report.

In July, the Hotshot crew had traveled 2,000 miles from Staunton, Va., to help dig fire lines for about a week around a 143-square-mile wildfire east of Billings.

At the campaign event with Mrs. Bush, Mr. Burns talked about the war on terrorism, saying a “faceless enemy” of terrorists “drive taxicabs in the daytime and kill at night.”

The campaign said yesterday that the senator was simply pointing out terrorists can be anywhere.

“The point is there are terrorists that live amongst us. Not only here, but in Britain and the entire world,” a spokesman, Jason Klindt, said. “Whether they are taxi drivers or investment bankers, the fact remains that this is a new type of enemy.”

Responding to Democratic complaints about Mr. Burns’ verbal gaffes, Republicans argued that a comment by Mr. Tester earlier this week was derogatory toward American Indians.

In an interview with the Seattle Times, Mr. Tester talked about the faith that he has in his staff and said, “Nobody has done anything to make me think they’re trying to tomahawk me.”

A spokesman for the Montana Republican Party, Brock Lowrance, said American Indians have long found “tomahawk” a derogatory term. American Indians are the state’s largest minority group.

At the fund-raiser, Mrs. Bush described Mr. Burns as a strong advocate for Montana farmers and families.

“In Washington, Senator Burns is a respected voice on the issues facing rural communities in Montana and across the nation,” Mrs. Bush said.