The Soviet Union announced today that it will stop making a rail-based mobile intercontinental ballistic missile, but did not commit itself to removing those already in place. Foreign Minister Eduard A. Shevardnadze made the announcement after two days of talks in this eastern Siberian city with Secretary of State James A. Baker III and before reporters had learned of Iraq's invasion of Kuwait. Both officials told reporters outside a guest house where they met that their 10 hours of discussions produced no major breakthroughs on what had been expected to be their main focus, the 12-year-old civil war in Afghanistan. But the announcement about the Soviet SS-24 missile indicated they had made some progress on arms control. The meeting, the 11th this year between Baker and Shevardnadze, was the most informal. The diplomats cruised the Angara River and went fishing. Shevardnadze landed a trout, but Baker came away empty-handed. Shevardnadze, standing along with Baker on a patio, said the Soviet military would cease production of the missiles on Jan. 1. He said the Soviet military would continue to deploy until 1991 ``not many'' of the missiles it has already produced. The removal of missiles already in place, he said, was a subject of negotiations between U.S. and Soviet teams in Geneva. According to the 1989 edition of the annual U.S. Defense Department publication ``Soviet Military Power,'' the Soviet Union began deploying the rail-based version of the SS-24 missile in 1987 and had about 58 of them. The SS-24 carries 10 warheads and has a range of abut 6,200 miles. Limits on mobile land-based missiles were one of the outstanding issues in START talks on slashing the superpowers' stockpiles of long-range nuclear weapons. Other bigger sticking points in the negotiations are curbs on modernizing the Soviet Union's biggest strategic missile, the SS-18, and the Backfire bomber, and on transfers of missiles to third countries. Shevardnadze did not say why the Soviet Union was taking the step, but the Kremlin is under pressure to cut its defense budget so it can spend the money on solving chronic economic problems. ``We welcome the announcement,'' Baker said before flying to Mongolia for the last stop on his four-nation Asian tour. He added, however, that ``It doesn't at this point, at least, change our negotiating position in START.'' U.S. officials indicated earlier this year that they might offer to give up plans for a rail-based MX missile if the Soviets give up the SS-24. Baker and Shevardnadze discussed the war in Afghanistan on Wednesday night and this morning, but the Soviet envoy told reporters, ``I cannot say we can report any kind of breakthrough on Afghanistan.'' The Soviets arm the Afghan government, while the Americans supply the guerrillas fighting it with military aid. Baker told reporters there were two main stumbling blocks to a settlement: _The makeup of a commission to ensure ``free and fair'' elections. _Which powers the current government, headed by pro-Soviet President Najibullah, might transfer to an interim government during elections so candidates are ensured a ``fair shake.'' Baker said Soviet and American experts will try to resolve differences over these points when they meet in Washington. He did not say when the meeting would take place. U.S. and Soviet officials reportedly have been working on a plan for Najibullah to hand over some power to a council of Afghan forces as a run-up to a nationwide election. The composition of the council is now in dispute. U.S.-backed Afghan rebels disagree about who should be on the council. Baker alluded to that at the news conference. ``We are moving closer together on Afghanistan. Having said that, I don't think you should take that to mean necessarily that those whose interests we have been allied with in the past are necessarily moving together,'' he said. In three meetings, including one Wednesday night in a river-side fishing lodge in the Siberian wilderness, Baker and Shevardnadze also discussed preparations for a third summit meeting between Bush and Gorbachev. Shevardnadze said not date had been decided for the summit, but that it would be held in Moscow. He also announced that Baker, U.S. Commerce Secretary Robert Mosbacher and leading American businessmen would travel to Moscow in September for talks on U.S.-Soviet economic cooperation. Baker indicated this primarily would involve ways of stimulating U.S. business investment in the Soviet Union, in dire need of Western help to cure its ailing economy. A Soviet source said that during their Wednesday morning meeting, Shevardnadze gave Baker a 15-page outline of areas for economic and scientific cooperation. The envoys meet next in Moscow on Sept. 12.