Officials in the Carter administration are studying sending a force of several thousand U.S. soldiers to police the Egyptain-Israeli peace treaty if the Soviet Union carries out its threat to veto United Nations forces for that task, administration sources said yesterday.

The administration still hopes to persuade the Soviet not to oppose a U.N. unit at the July Security Council meeting that will decide the issue. U.S. officials say they expect President Carter to make a personal plea for Soviet cooperation at his summit with Soviet leader Leonid Brezhenv in Vienna next month.

But the strong likelihood of a Soviet veto as a sign of opposition to the U.S.-sponsored treaty has triggered contingency planning within the adminstration for alternatives to the U.N. force that was supposed to police Israel's withdrawal from the Sinai peninsula over the next three years.

Uncertain at this point about domestic and Arab political reaction to a U.S. military force for the Sinai, the State Department reportedly is hoping to avoid that option by organizing a multinational force outside of U.N. auspices, probably with U.S. leadership and financing.

But initial informal reaction from other nations has not been positive. Most of them will continue to be cautious about supporting the treaty as long as Saudi Arabia, Kuwait and other oil-producing Arab nations maintain their strong economic campaign against Egypt, officials acknowledge.

The third option under study is for some form of policing of the agreement by the Egyptain and Israeli armies. The two countries reportedly have agreed to carry out the first phase of the Israeli withdrawal, which involves the return of the coastal town of El Arish to Egypt this month, under a joint patrolling arrangement. But Egypt is said to oppose any long-term joint effort.

The U.N. Emergency Force that has been deployed between the two armies in the Sinai since October 1973, under two U.S.-sponsored disengagement agreements, is composed of 4,000 soldiers from six foreign nations. The annual UNEF mandate is up for renewal in July by the Security Council.

The peace treaty signed in Washington last March by Egyptian President Anwar Sadat and Israeli Prime Minister Menachem Begin proposes that UNEF troops continue to patrol the buffer zones and report on suspected violations during the three-year phased withdrawal.

After the withdrawal is complete, the United States is obligated to organize an alternative peacekeeping force for the Israeli-Egyptian border if the United Nations is unable to do so.

The Soviet Union has joined Arab nations in attacking the treaty as a betrayal by the Carter administration and by Sadat of efforts for a comprehensive Middle East peace settlement that would include a solution to the Palestinian problem.

Soviet officials have conveyed to U.S. diplomats and journalists Moscow's determination to thwart a renewal by the Security Council of the UNEF mandate to police the treaty despite appeals from Washington for support.

If Carter does not succeed in getting Brezhnev to change the Soviet position in the Vienna talks, the administration has decided to put into effect immmediatley the treaty provision requiring Washington to organize an alternative force outside the U.N., officials said yesterday.

Officials at the State Department and the Pentagon emphasize that planning for the alternative force is still in a tentative phase, but the State Department's international affairs bureau has already sounded out other countries gently on a multinational force that would be about the same size as UNEF and that might include some U.S. troops.

Pentagon planners are reported to be considering a more mobile force that would be composed of U.S. soldiers only and that probably could be kept to half the size of UNEF because of its unified command structure. But strong opposition to a highly visible U.S. role in enforcing the treaty is coming from the State Department, according to official sources.

Administration officials expect congressional support for an increased presence in the Sinai if that becomes necessary to keep the treaty in effect. The United States has been contributing about one-fourth of the $76 million annual budget for the UNEF, and maintains a separate force of about 200 American civilians for electronic intelligence monitoring in the Sinai.

No cost estimates have been worked up for the three alternatives to UNEF being considered by the administration.