Major obstacles to an Iran-Contra trial of Oliver L. North were removed when the judge in the case sharply restricted the number of classified documents the former White House aide may use for his defense. By deciding to bar as evidence more than 90 percent of the classified documents North wanted to disclose, U.S. District Judge Gerhard A. Gesell greatly increased the chances that the case will go to trial, possibly late next month. Gesell's ruling diminishes the possibility that President Reagan's refusal to release virtually all the secrets sought by North would force dismissal of charges on the ground that the former National Security Council aide couldn't get a fair trial. The judge harshly rebuked North for demanding ``disclosure of masses of classified material which under no conceivable version of a defense could have any utility whatsoever.'' ``North, as a tactical matter, has taken an obdurate stand,'' Gesell said in an order issued Monday. ``If this tactic were permitted, there would be no trial.'' Gesell rejected a Nov. 14 list of 3,500 documents covering 30,000 pages of secrets that North had proposed as evidence under a provision of the Classified Information Procedures Act. But the judge denied independent counsel Lawrence E. Walsh's request to bar North completely from disclosing any secrets, saying a blanket prohibition would ``too severely restrict the defense.'' Instead, Gesell gave North until Jan. 3 to pick 300 documents from the Nov. 14 list that he wants to use as evidence. The documents will be censored for sensitive references to secret information by an interagency task force that reviewed Walsh's exhibits. The defense will be required to show the ``relevancy and materiality of each item and generalities will not be accepted,'' Gesell said. Gesell granted Walsh's request to censor some of the 300 documents the independent prosecutor wants to use as evidence to prove that North conspired to divert U.S.-Iran arms-sale profits to the Nicaraguan rebels. North had objected to virtually all of the deletions of sensitive information. But Gesell approved many of the changes, such as censoring the names of CIA agents, foreign officials and the sources of U.S. intelligence. He also approved Walsh's proposal to remove sensitive information from the orders by President Reagan approving the arms-for-hostage initiatives. But the judge made clear that he wants public disclosure of as much evidence as possible, denying requests to delete the names of Central American countries, Israel and Iran from documents in the case. Gesell noted that an earlier evidence proposal by North, on Aug. 1, also was rejected after a check of some of the documents listed showed it was ``obviously submitted in bad faith.'' Since then the court has repeatedly reminded North that he must provide specific information about how a document would help his case. Despite those warnings, the Nov. 14 notice contains ``ample evidence of North's attempt to frustrate the prosecution,'' the judge said. ``North's unwillingness to pay token respect to the court's requirement to provide detail appears to reflect his mistaken view that he is entitled to use classified materials at trial without indicating in any way the significance of that material to the prosecution and the court,'' Gesell said. ``This trial does not concern the reaction of various Central American countries to congressional legislation, the life history of a potential defector, the precise distribution of Sandinista forces at a particular time among various villages,'' Gesell said, listing the type of secrets North proposed to disclose. ``This is a case charging fraud and deceit on the United States, its chief executive and Congress, involving the use of arms profits in a manner allegedly unauthorized by the president,'' the judge said. ``It must remain focused on these issues, rather than be derailed by the myriad unrelated issues'' raised by North. North still has until Dec. 19 to submit an additional list of secrets he wants to disclose in testimony or from other documents not covered in the Nov. 14 notice. But Gesell's order made clear that he would reject a list that was similar to those previously filed. North's lawyers, meanwhile, sought a one-month delay in filing the next notice and argued that disclosing defense testimony will violate the former White House aide's right to a fair trial. ``Never before in the history of American criminal law has a court granted the prosecution such a one-sided bonanza of information about the defense case,'' lawyers Brendan V. Sullivan Jr. and Barry S. Simon said in the pleading filed Monday.