President Reagan, refusing to accept documentary evidence to the contrary, asserted last night that he never approved sending arms to the Iranian government of Ayatollah Ruhollah Khomeini but was instead dealing with nongovernmental factions seeking to establish "the kind of government that we once were closely allied to" there.

"We weren't dealing at all with the ayatollah," Reagan said in an interview with four television anchormen. "Now, I think he's as big a Satan as he thinks I am."

Reagan refused to accept the Feb. 26 finding of the Tower commission and Nov. 18 report by the congressional Iran-contra committees that U.S. arms sales to Iran were intended as a trade for Americans held hostage in Lebanon.

The final congressional report documented that U.S. negotiators dealt with representatives of Iran's prime minister and parliament speaker with Khomeini's approval.

It also showed that, in at least two instances, arms were delivered to representatives of "the Iranian revolutionary guard corps . . . the most radical elements in Iran."

However, the report added, "To the best of the committees' information, the president was never told that the United States was arming the revolutionary guard."

At times, Reagan has grudgingly acknowledged in prepared remarks that his administration traded arms for hostages.

Addressing the nation March 4, he said, "I told the American people I did not trade arms for hostages. My heart and my best intentions still tell me that's true. But the facts and the evidence tell me it is not . . . . What began as a strategic opening to Iran deteriorated in its implementation into trading arms for hostages."

Because he rarely holds news conferences or takes questions on the Iran-contra issue, there have been few opportunities since then to ask Reagan his feelings about what he did.

Last night, speaking without a script, Reagan returned to earlier formulations that overtures to Iran were part of an arrangement with anti-Khomeini forces and that arms sales were part of a U.S. effort to prove "good faith" with these elements to free the hostages.

Reagan denied that the transaction was a "scandal" and said, contradicting earlier statements, that it was "misconstrued . . . . that we were trading, as a ransom, hostages for arms."

The president refused to say whether he would pardon one of his former national security advisers, Rear Adm. John M. Poindexter, or former National Security Council aide Lt. Col. Oliver L. North, who are expected to be indicted.

Earlier, a White House spokesman said Reagan has provided sworn answers to written questions from independent counsel Lawrence E. Walsh, who heads the criminal investigation of the Iran-contra affair.

Staff writer Walter Pincus contributed to this report.