CAIRO, Egypt (AP) _ Hungary's ambassador said Wednesday his government has instructed Soviet authorities to stop letting Jewish emigres go to Israel via Budapest until the backlog is cleared of those already holding tickets.

Ambassador Erno Simonyi estimated it could take months before up to 2,500 ticketed Soviet Jews are transported to Tel Aviv.

Reacting to threats from Palestinian extremists, Hungary's national airline Malev announced last month it would transport no more Soviet Jews to Israel. Hungary later reversed the announcement for scheduled flights and fired Malev's manager, but a ban remained on charter flights for Soviet Jews.

Simonyi told reporters, ''The Hungarian airline is now taking without discrimination any nationals, including Soviet Jews. But we aren't taking any new passengers until those who already have tickets are transported.

''They are about 2,000-2,500, so it will take several weeks, probably months.''

He said Hungarian authorities also told the Soviet carrier Aeroflot not to issue tickets on Malev flights from Budapest to Tel Aviv.

Simonyi apparently chose to address the issue in Cairo to emphasize that the decision to continue flying Soviet Jews to Israel should not affect Hungary's relations with Arab countries.

As in the rest of the Arab world, emigration to Israel of thousands of Soviet Jews has caused an uproar in Egypt, the only Arab country at peace with the Jewish state.

Simonyi said ''some 1,000'' Soviet Jews have used the Budapest-Tel Aviv route since it opened last fall.

Palestinians and Arab governments fear a large influx of new Israelis will settle in lands Israel captured from Jordan and Egypt in the 1967 Middle East War.

Israeli officials say they expect up to 750,000 Soviet Jewish immigrants by the end of the decade.