Secretary of State George P. Shultz is sending his executive assistant, Charles Hill, to Israel next week for high-level talks, triggering speculation there that the United States may be preparing a new push for an international peace conference to resolve the Arab-Israeli conflict.

Department spokesman Charles E. Redman confirmed yesterday that Hill will visit Israel "for informal discussions on a variety of issues." Asked why Hill is making the trip instead of Richard W. Murphy, the assistant secretary for Mideast affairs, Redman replied: "He's the person who is available at this point; he works closely with the secretary on these matters."

However, in Israel, news of Hill's trip sparked widespread speculation that he will try to persuade Prime Minister Yitzhak Shamir to drop his opposition to the international conference sought by King Hussein of Jordan as an umbrella for Jordanian-Palestinian talks with Israel.

Israel's coalition government is deadlocked by disagreement between Shamir's Likud bloc, which strongly opposes the idea, and Foreign Minister Shimon Peres' Labor Party, which sees the international conference as a step to direct negotiations with Jordan.

The United States has sided with Peres but also has promised to take no action on an international conference without the agreement of the full Israeli government. Some reports from Israel said yesterday that Hill will seek to change Shamir's mind by offering U.S. guarantees that the Palestine Liberation Organization will be barred from the conference and that the conference will be structured to lead to direct Israeli-Jordanian talks.

However, diplomatic sources here agreed that it would be what one called "naive and simplistic" to assume that a mission of this type could induce Shamir to surrender his convictions. The same source said Hill's trip should be viewed as "a preliminary step to a first step -- an attempt to give Shultz an assessment by a trusted aide as to where things stand in Israel regarding the peace process and what avenues offer the United States the best chance of moving things forward."

But, the sources added, the mission has a special character compared with past fact-finding trips by U.S. officials because Shultz has entrusted it to someone who not only is well versed in Israeli affairs but also is identified closely with the secretary.

Before becoming Shultz's executive assistant, Hill served at the U.S. Embassy in Israel and was director of the State Department's office of Israeli affairs. In that capacity, he was the principal author of the Sept. 1, 1983, speech in which President Reagan revealed his comprehensive Middle East peace plan.

The latest proposal calls for the five permanent members of the U.N. Security Council -- the United States, the Soviet Union, Britain, France and China -- to convene an international conference that then would give way to negotiations between Israel and a joint Jordanian-Palestinian delegation.