JERUSALEM -- Despite initial government denials, Foreign Minister Shimon Peres has confirmed that he provided a written guarantee protecting the status of PLO offices in Jerusalem.PLO leader Yasser Arafat set off the controversy by disclosing the existence of an agreement on Jerusalem in Johannesburg on May 11, and rightist opposition leaders have been demanding an explanation from Prime Minister Yitzhak Rabin.The Oct. 11 correspondence had not been with Arafat but with Norway's late Foreign Minister Johan Jorgen Holst, who hosted secret Israel-PLO talks that led to the Sept. 13 accord."I wish to confirm that the Palestinian institutions of East Jerusalem ... are of great importance and will be preserved," Peres wrote.The letter, faxed to The Associated Press on Monday, also pledged the government would "not hamper" the activity of such institutions, "including the economic, social, educational and cultural, and the holy Christian and Moslem places."The controversy over the letter is embarrassing for the government because it comes at a time when Rabin has threatened to close PLO offices.Likud legislator Dan Meridor told Israel radio that the government's handling of the letter was a "scandal.""We are talking here about a commitment that I still don't know the contents of, but the attempts intended to hide it and the mistruths told by everyone who dealt with it, arouse deep concern that there is more to it than just excerpts from the parliament speech," Meridor said.