A congressional committee that will open public hearings Monday on the Iran arms and contra fund scandal has requested, but failed to get, key documents relating to the affair. Staff members have expressed disappointment at the White House's apparent lack of cooperation.

In late November, the House Foreign Affairs Committee requested the text of President Reagan's Jan. 17 finding that authorized the transfer of weapons to Iran, along with numerous other papers.

But two days before Reagan administration officials are to present their first public, nationally broadcast testimony on the scandal, committee Chairman Dante Fascell, D-Fla., said in a telephone interview that neither the finding nor any other White House document had been delivered.

Secretary of State George Shultz and former national security adviser Robert McFarlane have both agreed, albeit reluctantly, to testify before Fascell's committee Monday. Vice Adm. John Poindexter, the former national security adviser, and CIA Director William Casey are scheduled to face the committee Tuesday and Wednesday.

Shultz's appearance has taken on added importance amid revelations that the secretary personally persuaded a wealthy Asian sultan to donate several million dollars to the Nicaraguan rebels. The disclosures have revealed a relationship between the State Department and the private aid network that Lt. Col. Oliver North directed from the White House.

Shultz at first refused to testify before Fascell's 42- member committee under oath, arguing that as secretary of state his word should be good enough for the Congress, sources said. Fascell said Saturday, however, that Shultz had dropped his objections, realizing that he eventually would face subpoenas from select investigative committees in formation in both houses of Congress.

"I'm going to swear him in, " said Fascell, of Miami.

"We start out with a high regard for the man, " Fascell said. "Now what committee members will think of his positions . . . if he comes on as a good team player within the administration, I don't know."

Fascell said the objective of the House hearings is to "get our foreign policy mechanism straightened out so we can get back in business again."

Among other topics, staff members said they had been developing questions on the implication of the Iran initiative and contra fund diversion for U.S. involvement with rebels in Nicaragua and Angola, Mideast relations and U.S. arms export policies.

Besides Reagan's finding, the documents that Fascell's committee has requested include presidential directives to White House employees relating to the Iran initiative, directives to the CIA or other agencies instructing them "not to inform Congress" of the initiative, as well as documents showing financial transactions in the Iran affair.

Early last week, congressional sources said that White House officials told them that the documents would soon be forthcoming. By week's end, no documents had appeared, and skepticism about the White House's reasons appeared to be mounting.

"We're disappointed we don't have them, " a committee staff person said.

"One side of me wants to understand everybody's problem over there, " the source said, "but the president said he would cooperate. This is one of the key things he said he was going to do to help dissipate this thing."

Another congressional source said it appeared that the White House had not even "tasked out" the document requests to the executive agencies that have them.