Israeli Defense Minister Ariel Sharon said today that he has held secret negotiations with Lebanese officials that could lead to normal relations between Israel and Lebanon.

Lebanese officials in Beirut and Washington, however, denied that discussions had taken place between Sharon and Lebanese government representatives.

"This report is completely false," Lebanese Foreign Minister Elie Salem was quoted by United Press International as saying in Beirut. Salem said that Sharon had not met any government members and that there had been no direct talks between the Israeli and Lebanese governments, UPI reported.

In Washington, sources speculated that the Israeli minister may have talked only with officials of the Lebanese Forces, a Christian militia armed by Israel and close to the Beirut government, Herbert H. Denton of The Washington Post reported.

At the same time, U.S. officials, who had been pessimistic about the prospects of ending the deadlock over negotiations to withdraw foreign troops from Lebanon, were guardedly hopeful that Sharon's remarks could signal the beginning of a breakthrough.

Israel has not identified precisely the persons with whom Sharon reportedly talked in Lebanon, and few details of any content have been made public.

Such talks would be viewed as significant because Arab Lebanon does not recognize Israel and has resisted contacts that could be viewed as normalizing relations.

Sharon announced his "breakthrough" yesterday while on a surprise tour of Israeli-occupied sections of Lebanon. Today, in interviews, he expanded on the announcement, speaking in terms of "agreements" for an end to the state of war between Israel and Lebanon, an open border with the free flow of trade and tourism and "security arrangements" in southern Lebanon to guarantee Israel's northern communities against attack.

Other Israeli officials said Sharon's talks with unidentified Lebanese officials had produced "agreement in principle on all the matters that we wanted," although they conceded they did not know whether Sharon's understandings with the Lebanese were "watertight."

The Jerusalem newspaper Maariv, in its account of an interview with Sharon, said he had spoken with "representatives of the Lebanese regime." The newspaper Haaretz identified them as "Lebanese figures close to President Amin Gemayel" and said the talks were conducted "via Christian militia mediation," a reference to the Lebanese Forces.

According to reports here, Sharon's talks in Lebanon took place with the full backing of Israeli Prime Minister Menachem Begin and the knowledge of Foreign Minister Yitzhak Shamir.

Some officials in Washington read Sharon's remarks as a hopeful sign of at least a changed attitude within the Israeli government.

"The state of play is more fluid," one U.S. official said. "There's just a lot happening that just may be, just may be more hopeful."

The view in Washington had been that Sharon and allies in the Israeli Cabinet were the major obstacles to progress on the withdrawal talks.

According to Israeli officials, if the agreement Sharon says he has reached with Lebanon in principle can be nailed down in detail it will make unnecessary high-level meetings between Israeli and Lebanese officials in Beirut and Jerusalem. Lebanon has resisted Israel's demand for such meetings, saying it would not come to Jerusalem, which it considers an occupied city.

All that would then remain, according to the Israeli view, is for U.S. envoys Philip C. Habib and Morris Draper to win agreement for a Syrian and Palestinian troop withdrawal from Lebanon, upon which the Israeli Army would also leave.

The Israeli Cabinet is to meet Sunday and discuss both Sharon's initiative and Habib's proposals for a troop withdrawal.

Sharon was widely reported to be angered last week when, during a visit to the United States, he was not invited to Washington for meetings with Reagan administration officials. Today, he accused the administration of delaying the Lebanon negotiations by attempting to link them to President Reagan's initiative for a peace settlement in the occupied West Bank and Gaza Strip.

Haaretz today quoted Sharon's supporters as saying the defense minister, in reportedly achieving a breakthrough, had "evened the score" against U.S. officials.

Sharon came under sharp criticism after the massacre of Palestinian refugees in Israeli-occupied West Beirut and is considered one of the most vulnerable figures in the Israeli investigation of the massacre. In recent months he has been courting political support and would clearly benefit if credited with achieving Israel's goal of "normal relations" with Lebanon.

In an interview held yesterday and published today in Maariv, Sharon said that as a result of his talks with the Lebanese, "a situation has been created which will guarantee Israel's political gains" from the invasion of Lebanon.

Sharon's optimistic predictions ignored or glossed over the details on a number of sensitive issues in any Israeli-Lebanese agreement, among them the future role in southern Lebanon of the Israeli-supported militia of Saad Haddad.