WASHINGTON - The National Rifle Association has apologized for a recent fund-raising letter that described some federal agents as "jack-booted thugs."

"I really feel bad about the fact that the words in that letter have been interpreted to apply to all federal law-enforcement officers," NRA Executive Vice President Wayne LaPierre said in a telephone interview from Phoenix.

"If anyone thought the intention was to paint all federal law-enforcement officials with the same broad brush, I'm sorry, and I apologize," LaPierre said yesterday.

The apology drew cautious approval from Attorney General Janet Reno today.

"I trust that the level of communication now will go forward in a thoughtful and respectful way," she said. But later she said, "They like to call names rather than to pursue matters in a thoughtful and constructive way."

LaPierre's apology comes after a week of steadily mounting criticism of the NRA. It began May 10 when former President Bush revealed he had resigned from the group to protest the letter. Earlier this week, President Clinton joined the critics and praised Bush.

Rep. Charles Schumer, D-N.Y., a longtime gun-control advocate, today introduced a House resolution urging the NRA to present to its members a statement condemning the use of inflammatory language by the group's leaders and pledging not to use it in the future.

Republican Senate Leader Bob Dole, a longtime NRA member, said he was "pleased" by LaPierre's apology.

"The NRA has done the right thing. They should not have used some of that language in the first place," Dole said on the Senate floor.

LaPierre insisted that the fund-raising letter was intended to criticize only isolated actions, primarily involving the Bureau of Alcohol, Tobacco and Firearms.

But at least one section of the letter offered a more sweeping condemnation of federal law-enforcement efforts.

The letter, sent to the NRA's 3.5 million members in March over LaPierre's signature, referred to federal law-enforcement agents as "jack-booted government thugs" and said that "in Clinton's administration, if you have a badge, you have the government's go-ahead to harass, intimidate, even murder law-abiding citizens."