Soviet officials, working to salvage a U.S.-Soviet aviation agreement in time for next week's Bush-Gorbachev summit, will come to Washington this weekend in an effort to negotiate the last sticking point, U.S. sources said yesterday.

The problem involves the percentage of U.S. airline tickets to be sold in rubles in the Soviet Union. If it can be solved, air travel between the countries would increase dramatically from the current handful of Aeroflot and Pan American World Airways routes.

"We have an agreement that is 98 percent done," said a source involved in the negotiations. But the unresolved economic problem is as important as "the battery in a transistor radio." There will be no agreement without it, he said.

The proposed agreement calls for an increase in the number of airlines that may fly between the two countries, the number of cities that may be served and the number of flights. An annual minimum of 100 transatlantic charter flights would also be guaranteed.

For years, U.S.-Soviet air travel has been limited to a handful of weekly flights by Pan Am and the giant Aeroflot. Only New York, Washington, Moscow and Leningrad have been served.

The new agreement would increase the number of U.S. carriers to six passenger and/or cargo airlines. Aeroflot's schedule could be expanded, and a second Soviet airline -- envisioned as competition for Aeroflot -- would also be eligible for U.S. routes. Transatlantic routes would be increased and Pacific routes added.

The new U.S. cities to be served by Soviet carriers would be Anchorage, Chicago, San Francisco and Miami. Miami is expected to be a stop on a Soviet route to South America.

In the Soviet Union, the new eligible cities would be Kiev, Minsk, Magadan, Khabarovsk, Tbilisi and Riga in Latvia.

Several U.S. airlines have expressed interest in the routes, particularly American Airlines, which wants to fly to Moscow and Leningrad, and Delta, which wants to fly to those cities plus Tbilisi in Soviet Georgia. Pan Am wants additional routes, and other airlines such as United and Northwest are watching the talks.

The State Department estimated yesterday that the agreement would triple travel between the two countries.

The sticking point has been economic rather than operational. U.S. airlines want to sell as many tickets as possible in rubles, increasing their access to Soviet citizens who have no dollars or other hard currency. Initially, the airlines sought to use the rubles to buy services in the Soviet Union, reducing their need for rubles at the inflated official exchange rate.

During the months-long talks, the negotiators agreed that a percentage of U.S. air capacity would be sold in rubles by Aeroflot, which would act as agent for U.S. airlines. Aeroflot then would pay U.S. airlines in hard currency.

The problem was the exact percentage. The United States first suggested 15 percent, then came down to 11 percent. The Soviets said 2 percent and stuck to that position.

Yesterday, the Soviets "indicated a desire to come to Washington this weekend . . . and see if we can get an agreement in place before the summit," a source said.