Former Treasury secretary William E. Simon and former U.N. ambassador Jeane J. Kirkpatrick are among leaders of an organization that seeks to raise $14 million for Nicaraguan rebel forces and was launched this week with a $100,000 contribution from the Unification Church.

The Nicaraguan Freedom Fund, founded by The Washington Times, plans to raise the funds for such "humanitarian aid" as food, clothing and medical supplies that it will supply to the "contra" rebels, according to the group's leaders.

Times Editor-in-Chief Arnaud de Borchgrave, who announced the campaign in a front-page editorial Monday, said yesterday that he recruited Simon as the group's chairman and Kirkpatrick and writers Midge Decter and Michael Novak to join Simon on a four-member board of directors.

Since he announced formation of the group, de Borchgrave said, he has been flooded with telephone calls and letters, including many pledging or sending funds.

Col. Bo Hi Pak, top deputy to Unification Church leader the Rev. Sun Myung Moon and president of the newspaper's parent company, made a $100,000 pledge Sunday and has provided the check, de Borchgrave said.

In addition, he said, Kirkpatrick has pledged $20,000 in lecture fees, and former member of Congress and ambassador Clare Boothe Luce $1,000.

"It's been really extraordinary," de Borchgrave said. "I would imagine that, judging from the response so far and the ongoing worldwide interest, . . . the target will be reached pretty quickly."

Simon said in an interview that he agreed to head the group because "I felt very strongly about the cowardice of Congress in their vote on this question. I think support for the freedom fighters is critical."

Asked if Unification Church involvement would compromise the campaign, Simon replied, "They're not involved. This committee is separate and distinct from the newspaper and the church, and I'm the head of it, period."

The campaign, which starts two weeks after Congress rejected President Reagan's request to fund aid to the rebels, appears to be the most ambitious private effort to raise money for the guerrillas fighting the leftist Sandinista government, according to some of their supporters.

Since Congress ended covert assistance to the rebels last year, several conservative groups, such as the World Anti-Communist League and United States Council for World Freedom, have engaged in independent drives to funnel miliary and other aid to the rebels.

The overall scope of such private aid has been difficult to measure, in part because many of the groups have described their efforts as raising humanitarian aid to refugees in Honduras, where many of the families of Nicaraguan rebels are living. In addition, federal law bans fund-raising within the United States for weapons to be sent overseas.

The White House has declined to comment on the private fund-raising, saying it neither "encourages nor discourages" such efforts.

Simon said he talked late yesterday with White House communications director Patrick J. Buchanan, who told him "they appreciated our efforts and thought what we were doing was very constructive."

Buchanan said that he called Simon to tell him "he was doing a good job and a constructive one" but that this did not reflect an official administration position.

"I haven't talked to anybody about it," he said. "Bill Simon is an old friend, and I just picked up the phone to say congratulations."