Senate Minority Whip Wendell H. Ford (D-Ky.), fielding telephone calls on a Louisville radio talk show yesterday, used the racial slur "nigger" in a conversation about the pending budget agreement.

An apologetic Ford said he thought the caller had used the word first, and was "so shocked and offended" that "I shot back at him."

Spokesmen at WHAS radio in Louisville said Ford, the Senate's second-ranking Democrat, appeared on its "Jane Norris Show" between 10:30 and 11 a.m. Senators often tape or record live radio shows from Washington.

In the "Jane Norris" tape, played by WHAS for The Washington Post, Ford discusses with an unidentified male caller the seven-year budget agreement now pending before Congress.

Ford said later in an interview that he was repeating the Democratic contention that tax cuts in the GOP budget package would disproportionately benefit the rich, prompting the caller to say: "I'm not near as rich as you, senator."

"Well, I'm not nigger rich, either," Ford replied.

"I said, not near as rich' as you," the caller said, correcting Ford.

On the tape, the phrase "near as rich" is not clearly enunciated, and Ford said later in an interview that he suspected the caller was using a cellular phone. "Even the host of the show said it could have been mistaken for what I thought he said," Ford said.

In a statement recorded for WHAS, Ford said, "I thought the caller used an offensive racial epithet. I was so shocked and offended that I shot back at him, and I repeated what I thought the caller said to emphasize how offensive it was to me." Ford said later he had "no idea" what the offending phrase meant, and had never heard it previously.

"I'm just sick about it," said Ford. "I regret it deeply and I apologize for it." CAPTION: SEN. WENDELL H. FORD