The United Sates, Egypt and Isreal have summoned their military experts here tomorrow to work out operational details of a multinational peacekeeping force that would place American troops permanently on guard in the Middle East for the first time.

The military meeting and other developments indicate that the largest procedural and political hurdles have been corssed, with the three nations now moving rapidly toward creating an international unit to monitor the Sinai after the scheduled withdrawal of Israeli troops next April.

The State Department announced that the military meeting to be held here Monday through Wednesday, followed a U.S. "conclusion" that the United Nations will not sponsor a peacekeeping body for the Sinai as envisioned in the Egyptian-Israeli peace treaty.

In view of this determination, the State Department statement said, the United States will take the steps necessary to establish and maintain a multinational force outside a U.N. framework. This is in keeping with a commitment given Israel by President Carter during the peace negotiations.

After this week's meeting of military experts, the State Department said, political officials of the three nations will meet on the issues a few days later in Giza, Egypt. Final agreement on the force is expected before the June 30 Israeli election.

A draft copy of a proposed agreement to establish the force will be placed before the military experts tomorrow by the United States, which has drawn it up after discussions with Egypt and Israel.

The draft calls for a force of 2,000 to 2,500 men, organized in three small battalions, according to informed sources.

One of the three would probably be a highly mobile but lightly armed American infantry battalion. The aim of the force's organizers is to obtain the rest of the multinational force from such nations as Canada, Australia, New Zealand and others approved by Egypt and Israel.

The cost of the international force has been roughly estimated, in discussions with members of Congress, at $50 million a year. There is little doubt that the United States will pick up most of the costs, directly or indirectly.

Some members of Congress have expressed concern about placing U.S. military forces permanently in an exposed position in a volatile part of the world where several previous wars were fought.

The House Foreign Affairs Committee, in legislative languaage in the process of being adopted, has specified that the United States cannot finance or participate in such a force "unless and until Congress has thoroughly reviewed such a proposal and has enacted legislation expressly authorizing such activity." But in the end, Congress is expected to go along.

In several months of simi-public jockeying, Israel argued for the largest possible peacekeeping force with the largest percentage of Americans, while Egypt argued for a smaller force with the minimum American participation. A 2,000- to 2,500-man force, with a strong minority of Americans, is reported to be acceptable to both sides.

Egypt also insisted that a serious effort be made to persuade the United Nations to play the sponsoring role set forth for it in the Israel-Egyptian treaty. But Cairo increasingly was convinced that his was unlikely, in part because of a potential Soviet veto, so Egyptian deplomats began negotiating in New York for a letter from the U.N. Security Council chairman stating the U.N. sponsorship is politically impossible. Such a letter is likely to be arranged this month, diplomats said.

Another Egyptian concern, which apparently was laid to rest of Secretary of State Alexander M. Haig Jr. in conversation last month the President Anwar Sadat, is that the American contingent of the peacekeeping force might take a regional security role as part of the proposed U.S. rapid deployment force.

Haig is reported to have emphasized that the only mission of American troops in the Sinai will be peacekeeping in that area under the terms of the Egyptian-Israeli treaty. A similar limitation is being written into the charter of the planned multinational force, according to U.S. sources.