The Israeli government next week will submit a request for $2.9 billion in U.S. military and economic aid for fiscal year 1982. The figure is less than was requested last year but well above what Israel has received in each of the last three years.

Government officials said the reduced aid request was prompted by an improved balance of payments, coupled with an increasingly realistic appraisal of what is likely to be approved by the White House and Congress.

Since 1977, U.S. aid to Israel -- the highest to any country in the world -- has been about $1.785 billon, including $1 billion in military aid and the rest in economic support.

This year approximately half the military aid was in the form of a grant and half a loan, while two-thirds of the economic aid was a grant and the remainder a loan.

Officials said Israeli Ambassador Ephraim Evron will submit the aid request next week to Secretary of State Edmund Muskie. A team of Israeli economists, led by Finanace Minister Yigael Hurwitz, will go to Washington next month to elaborate on the request, which is expected to be submitted to Congress by the end of the year. The request is for the fiscal year beginning Oct. 1, 1981.

While U.S. policy has been to reassure Israel that military and economic aid will never be used as leverage in political negotiations, some observers here believe that the stalled West Bank autonomy negotiations, coupled with the American presidential elections this fall, will mean tougher sledding for Isreal's request.

Most Israelis believe the American posture toward Israel hardens considerably in a postelection year because of the reduced dependence by presidents on support from the American Jewish community.

Last year, Israel submitted a record $3.45 billion aid request, basing the higher figure largely on skyrocketing fuel costs stemming from the return of the Sinai Peninsula oil fields to Egypt under the peace treaty. This year Israel is spending about $2.3 billion on oil imports, about $900 million more than the previous year.

The government's record request last year was also attributed to the growing Middle East arms race and the 20 percent increase in the dollar cost of U.S. arms.

For the 1981 fiscal year, the Carter administration granted a special appeal by former Israeli defense minister Ezer Weizman and added $200 million to the aid, which was matched by an additional congressional foreign aid appropriation of $200 mllion. As a result, Isreal in 1981 is assured of receiving $1.4 billion in military aid and $875 million in economic support. o

Moreover, under a special aid package resulting from the Camp David peace accords, Congress approved in March 1979 an additional $3 billion -- $800 millon of it in grants -- for building new airbases in the Negev Desert and redeploying its armed forces form the Sinai.

Egypt received $1.5 billion in military aid as a result of Camp David. This year Egypt is receiing $1.1 billion in economic support.

Meanwhile, officials of the embassies of Costa Rica and Ecuador here denied published reports that they are moving to Tel Aviv to protest the recent Israeli parliamentary vote to perpetuate Israel's control over all of Jerusalem, including the eastern sector captured in 1967.

The Israeli Foreign Ministry also said it had received no information on the reported moves. Venezuela and Uruguay have announced plans to move to Tel Aviv because of the Jerusalem issues.