President Clinton has further strained relations with Democratic leaders in Congress by promising to "personally repudiate" Democratic candidates during elections next year who try to attack incumbent lawmakers for supporting the North American free-trade agreement.

Meanwhile, the Clinton administration was close Friday to completing a plan for funding the Nafta that would rely on two accounting maneuvers: reducing the time that banks are allowed to hold certain taxes, and using the president's existing tariff-cutting authority to shave a billion dollars off the Nafta's price tag over five years.The banking change would raise another billion dollars over five years, a fee on incoming rail and truck traffic would raise $162 million, and the administration hopes to raise about $150 million more through a tightening of tax-reporting requirements for sports gambling, according to congressional sources.

To try to attract votes for the trade pact, Clinton aides are considering a provision in the Nafta bill that would advise the president to abrogate the agreement after three years if it is judged to have caused excessive job loss in the United States. Republicans will likely fight such a plan and House majority leader Richard Gephardt - a Nafta opponent - said Friday that "I don't think it solves the problem."

Mr. Clinton's threat to Democrats - delivered at the White House last week to Republican U.S. Rep. Peter King of New York - sent ripples through the House leadership Friday. Republican House leaders, looking to give political cover to members inclined to vote for the Nafta, welcomed the president's commitment.

Rep. Newt Gingrich of Georgia, the second-ranking Republican in the House, heard the president repeat the pledge at a White House meeting Friday and said he expected to get it in writing.

"With that kind of letter from the president, I think we can neutralize this issue entirely," said Mr. Gingrich, who is expected to be named House minority leader next year.

The news was not received nearly as well at the Democratic Congressional Campaign Committee, the body that funds and coordinates House campaigns.

DCCC Chairman Vic Fazio, D-Calif., who supports the Nafta, is nevertheless reportedly furious about the president's promise and the trouble it poses for the many Democrats who will run against sitting Republicans next year on anti- Nafta platforms.

His office declined comment on Friday, but a party source said the Clinton promise has become a major liability. "How can the president, the head of the party, dictate what's going to be in a campaign?" the source asked.

Peter King, a lawyer from the Long Island suburbs near New York City, is an unusual person to trigger such a partisan backlash. He is as unassuming and polite as any member of Congress, said colleagues, in the old style of freshman lawmakers who follow their leaders and avoid making waves.

When he was ushered in with 10 colleagues to see President Clinton last Tuesday, it was his first real meeting with the president. "I'd seen him a couple of times before, receiving line kind of stuff," the congressman said.

With Mr. Clinton's full attention, he asked a question that he said had been bothering him a lot in recent weeks.

"I said: 'Mr. President, I support the Nafta, but I've got a very practical political question. Democrats in my district are going to go after me if I vote for the Nafta, and the Perot people will also. What kind of assurances can you give about protecting me?' "

Mr. Clinton responded, "I will personally repudiate any Democrat who uses this against you," Mr. King said. "I made sure I wrote that down right away."

The congressman said he was grateful for the promise, which he thinks the president will keep, because the Nafta has been a difficult issue in the New York metropolitan area, where most lawmakers oppose the agreement.

The second- and third-ranking House Democrats - Reps. Gephardt and David Bonior, D-Mich. - are opposed to the Nafta but have said they want to keep their differences with the president from affecting overall relations with the White House. Spokesmen for both said they had no comment on the president's pledge.

Rep. Gingrich said Democratic leaders opposed to the Nafta should have expected the president to make the kind of promise he made last week.

"They made a major mistake taking on their president," he said.

Bill Daley, the Chicago power broker tapped by Mr. Clinton to lobby Congress on the Nafta, said he did not think the pledge would harm relations with Democrats opposed to the trade agreement.

He said Mr. Clinton would not be endorsing Republicans over Democrats as a result, but that the president hoped "the Nafta would not be a litmus test in the future."