President Clinton refused yesterday to provide witnesses or key documents to members of Congress investigating his decision to grant clemency to Puerto Rican nationalists, raising tensions between the White House and a Republican-led Congress that is showing a renewed appetite for probing the executive branch.

The White House's invoking of "executive privilege" infuriated GOP leaders, who have accused the administration of withholding information on a variety of issues since Clinton took office. Yesterday's sharp exchanges, and the new round of investigations by several congressional committees, show that the climate of accusations surrounding Clinton did not evaporate with his impeachment acquittal, but instead will dog him through the final days of his presidency.

Targets of the new congressional probes are the administration's role in Russian banking improprieties, the 1993 siege at Waco and last month's decision to free a dozen members or sympathizers of the Puerto Rican terrorist group FALN.

White House aides and other Democrats warn that the probes could come back to haunt the Republicans, accentuating an image of a vengeful party bent on harassing the president. But while Clinton has no more campaigns to run, the investigations could also cause problems for the two politicians most closely associated with him.

Vice President Gore, who's running for president, could be tarnished by the probe into Russian finances. He has been the administration's point man on relations with President Boris Yeltsin's regime, which critics have accused of mishandling foreign aid from the International Monetary Fund and other institutions.

Hillary Rodham Clinton, meanwhile, has seen her New York Senate bid buffeted by the Puerto Rican clemency issue, in which Republicans have accused the president of trying to win support for his wife among New York's Puerto Rican voters. As the controversy swelled, the first lady said the clemency offer should be rescinded, but most of the inmates in question were released last week.

Republicans say they are investigating legitimate, important matters, not trying to score political points. Beginning with the investigations of the White House travel office firings and White House deputy counsel Vincent Foster's suicide, they say, the administration all too often has withheld information when Congress tried to perform its oversight duties.

Yesterday, Rep. Dan Burton (R-Ind.), chairman of the House Government Reform Committee, rebuked the White House for rejecting his panel's request for documents and witnesses pertaining to Clinton's decision to grant clemency to the Puerto Ricans. "The president has a moral obligation to the American people to explain why he let terrorists out of prison," Burton said.

The White House returned fire, accusing Burton of seeking political revenge against a president the Republicans could not drive from office. "We're now hearing and getting subpoenas from a committee chairman who -- I don't really know what legislative accomplishments he's had in his tenure as chairman," White House press secretary Joe Lockhart said. "But I can tell you that we've gotten something like 700 subpoenas from him. He has publicly stated that his mission is to get the president. . . . This is about trying to pursue a political agenda."

In a six-page letter to Clinton yesterday, Attorney General Janet Reno argued that the White House has strong legal arguments for refusing to provide key memos or witnesses to explain the clemency decision, a power the Constitution assigns solely to the president.

"The White House staff and the Department of Justice act as confidential advisers to the president as part of the clemency review process, and executive privilege has long been understood to protect confidential advice generated during that process," Reno wrote.

Burton's committee remains the most active House panel, investigating not only Waco and the FALN decision but also the 1996 campaign finance scandal; Chinese espionage; and allegations the Clinton administration has retaliated against whistle-blowers.

House leaders have been sharply critical of Clinton's and Gore's approach toward Russia, and three panels are looking at the issue, including the House Banking and Financial Services Committee, the House International Relations Committee and the Joint Economic Committee.

On the Senate side, the Judiciary Committee has been feuding with the administration on several fronts: The panel plans to vote next week on whether to issue subpoenas in connection with Clinton's clemency offer and has threatened to unilaterally release a redacted version of Reno's closed-session testimony on the department's investigation of possible espionage by nuclear scientist Wen Ho Lee.

Senate Judiciary Committee Chairman Orrin G. Hatch (R-Utah) is also discussing the creation of a bipartisan Waco task force with Sens. Arlen Specter (R-Pa.) and Patrick J. Leahy (D-Vt.).

Judiciary is not the only active panel on the Senate side, however. A Foreign Relations terrorism subcommittee is also investigating the FALN flap, while the full committee will hold hearings next week on the administration's Russia policy.

Republican investigations of Clinton are nothing new, of course: In June 1998, House Democrats estimated that the GOP had spent $17 million on 50 probes of the administration, 38 of which were going on at the time.

But in many ways, the sudden burst in investigative activity underscores how the already-strained relations between Congress and the White House have only worsened since the impeachment proceedings ended this winter.

Specter, a moderate who has been critical of Reno during her tenure, said the Senate's relationship with the Justice Department "has been eroding day by day until it's reached the point of absolute frustration."

"The attorney general makes a standard answer: `I'll take that into consideration and get back to you,' and she never does," he added. "We need to issue subpoenas and we need to go for contempt citations because they have stonewalled us."

But White House chief of Staff John D. Podesta said: "At this point they are kind of like Ahab: They do it for hate's sake. . . . It's a lack of an agenda on their part. Members like Chairman Burton just live for these partisan investigations. . . . But I think the American public is sick of it."

American Enterprise Institute resident scholar Norm Ornstein observed that investigations provide Republicans with an opportunity to make some political inroads while their top legislative priorities, such as their $792 billion tax cut package, are stymied. "They need to follow a course here and figure out some way to be on the offensive," he said.