The chairman of the House Iran-Contra committee is demanding a formal explanation from the White House on why his panel never received two key documents suggesting that George Bush was involved as vice president in setting up a secret "quid pro quo" deal with Honduras to aid the Nicaraguan rebels, according to a letter obtained by the Los Angeles Times.

Rep. Lee Hamilton, D-Ind., who made the demand in a letter to White House counsel C. Boyden Gray, said that an extensive review of committee files over the past week indicated that Congress was denied at least two of the documents that have since turned up at the trial of former White House aide Oliver L. North.It is the first time in the long saga of the Iran-Contra affair that any member of Congress has accused the Reagan administration of withholding evidence in the probe.

Despite strenuous efforts to determine whether Bush participated in the scandal, members of the investigating committee never succeeded in tying Bush directly to President Reagan's efforts to provide the Contras with military assistance that had not been approved by Congress. The House and Senate committees were disbanded at the end of their inquiry in 1987.

Hamilton asked Gray, who also served as Bush's counsel when he was vice president, to "undertake an immediate review to determine whether documents were withheld from the Iran-Contra committees and to identify such documents, if any, to me and explain why they may have been withheld."

White House officials had no comment on the request, according to a spokesman. Bush himself has refused to discuss the information in the documents, insisting that any remarks by the president might jeopardize a fair trial for North. North's case goes to the jury next week.

Although Hamilton's letter did not accuse the administration of trying to cover up Bush's involvement by withholding the documents, he has made it clear that he thought the material would have prompted the committee to explore Bush's role in arranging the deal with Honduras.

"The documents clearly suggest that then-Vice President Bush, now President Bush, was involved in the quid pro quo arrangements with Honduras," Hamilton told CBS Thursday. "I don't think the documents prove that, but they clearly suggest it. And it would be apparent from those suggestions that he was more `in the loop' than he has thus far stated."

Hamilton said that the two documents in question were clearly within the scope of the committee's investigation and also within the realm of the committee's request for relevant document from the White House.

"A major focus of the investigation, of course, was: `What was the role of President Reagan? What was the role of Vice President Bush in these events?' " he said.