The Israeli government decided today to seek unspecified changes in the latest American proposal to break the deadlock in the negotiations on an Israeli troop withdrawal from Lebanon.

Israeli television reported tonight that officials close to the talks said the changes sought were minor, a point underscored earlier in the day by a source close to Prime Minister Menachem Begin who called the changes "not radical." Israeli officials, however, refused to discuss the details of the changes, which were decided on by a steering committee headed by Begin and including Defense Minister Ariel Sharon and Foreign Minister Yitzhak Shamir.

According to western diplomats in Beirut, the Lebanese also have agreed to the American proposed agenda with "minor reservations," Washington Post correspondent Herbert H. Denton reported. These diplomats said the U.S. proposal was for Israel and Lebanon to agree to an agenda that contains both sides' proposals with no order of priority, allowing negotiators for both countries to bring up whichever issue they wish first.

Amid signs of growing impatience among all the negotiators, the Israeli, Lebanese and American delegations are to meet again Thursday in the northern Israeli town of Qiryat Shemona to discuss the U.S. ideas for breaking the stalemate. It will be the sixth meeting since the twice-weekly talks began on Dec. 28.

At about the same hour Thursday morning, U.S. special envoy Philip C. Habib is scheduled to meet with Begin and reportedly will deliver a message from President Reagan on the importance of accelerating the troop withdrawal talks.

Habib has publicly denied that the United States intends to pressure Israel into dropping its demand that the troop withdrawal negotiations also lead to a form of normal relations between Israel and Lebanon. But the sense of frustration in the Reagan administration over the continuing stalemate, acknowledged by diplomatic sources here, was underscored by reports, published in Time magazine and widely circulated in the Israeli media today, that the administration is considering postponing Begin's scheduled trip to Washington next month if there has been no progress in the talks with the Lebanese.

The report remains unconfirmed, but it nonetheless provoked a sharp reaction today from Uri Porat, Begin's chief spokesman, who called the idea of postponing Begin's meeting with the president "nothing but gossip spread to cause hysteria."

The sense of urgency and impatience surrounding the troop withdrawal talks is being fueled by several factors. The United States sees the Israeli-Lebanese stalemate as a major stumbling block to progress on Reagan's broader initiative for an overall peace settlement in the occupied West Bank and Gaza Strip.

Jordan's King Hussein, whose participation in negotiations based on the Reagan plan is considered vital, may return to Washington soon, with Begin scheduled to follow in February. But Hussein is unlikely to agree to join broader negotiations if there is still no progress in the troop withdrawal talks, while the administration clearly does not want the president's meeting with Begin to be dominated by the situation in Lebanon at the expense of the overall peace initiative.

The accelerated pace of Israeli settlement of the West Bank has added to the sense that time has almost run out on the chance for any negotiated agreement involving the territory.

The Israelis went to the last meeting with the Lebanese and Americans, held Monday in the Beirut suburb of Khaldah, also prepared to demand changes in a U.S. proposal to resolve the agenda dispute. But according to the Israelis, the Lebanese opened the meeting by announcing their rejection of the U.S. plan, whereupon Morris Draper, head of the American team, made a new proposal.

It is this second U.S. proposal that is to be discussed Thursday in Qiryat Shemona and in which both Israel and Lebanon are seeking changes.

Israeli officials characterized Draper's latest proposals, as they had the first, as a "good basis for discussion," but said that "certain changes are necessary for this to become practical."

The dispute over the agenda centers on Israel's insistence that Lebanon agree to normal relations with Israel, including an open border and the free flow of trade and tourism, in return for an Israeli troop withdrawal from the southern third of the country. The Lebanese, fearful of the reaction among the country's Moslem majority and throughout the Arab world if they agree to formal ties with Israel, want the talks to concentrate on the troop withdrawal issue and Israel's demand for "security arrangements" in southern Lebanon.

Western diplomats in Beirut told the Post's Denton that the term "normalization," which the Lebanese object to, will not be on the agenda. Instead, they said, the words "framework of future relations" have been substituted.

Habib and Draper arrived in Israel yesterday and spent today in private consultations. Habib is to go on to Beirut after his meeting with Begin, but his exact schedule has not been set.