THE Baltic republics are officially free after more than a half-century of Soviet occupation. The city Czar Peter the Great built as his window on the West has shed the image of the birthplace of the Bolshevik revolution and restored its historic name of St. Petersburg.These decisions, made last Friday, are symbolic markers of the great historical drama unfolding in what is now called the "former Soviet Union." But these are relatively easy steps, impelled by the collapse of the old regime. Now the men who make up the new Soviet leadership are buckling down to a far more trying task - how to keep what remains of the Soviet Union together and avert economic catastrophe. The Soviet leadership met on Friday to begin implementing the decisions of the emergency meeting of the Soviet legislature last week on forming a transitional administration. Until the republican governments make their decisions on whom to send to a new union parliament and to a new interrepublican economic committee, the country is being managed by the interim team set up in the days after the failed coup. At the top is the State Council, the new collective leadership of the Soviet confederation, grouping Soviet President Mikhail Gorbachev and the heads of the 10 republics who have opted, for now, to remain in the union. The State Council met early Friday, where the decision to recognize the independence of the Baltic states was finally formally adopted. Following the meeting, Mr. Gorbachev issued a decree stating that until the interrepublican group was established, the committee for management of the national economy, formed after the coup and headed by Russian republican Premier Ivan Silayev, will act in place of the former Cabinet. The immediate priority of the interim government is to conclude an agreement on economic union, one that could embrace all 15 former Soviet republics, including the three Baltics, and potentially even their former allies in Eastern Europe. At the State Council meeting, the deputy head of the economic management committee, radical economist Grigory Yavlinsky, reported on progress toward that goal. Mr. Yavlinsky told the State Council, according to the Tass news agency, that a draft treaty of economic union is finished and that all the republics have agreed to send representatives to Moscow to finalize the text. According to reports, the treaty includes agreements on a range of issues including monetary policy, financial relations, trade, and foreign debt and credits. Yavlinsky has repeatedly expressed his belief that there must be a unified Soviet economic space, with common monetary and financial policies, if there is to be any hope for reform or for restoring economic stability. He also stresses that without this, it will be difficult to receive Western aid. "We have to ask the question of whether the republics are going to do something together or not," Yavlinsky told a meeting of the Geneva-based World Economic Forum in Moscow last week. "Only in answering this can we start negotiations with the G-7 [the Group of Seven leading industrial nations]." "There are a lot of things possible to do," Yavlinsky continued. "Privatization measures can be implemented at all levels: such things as independent banks, a reserve system, a federal reserve system, liberalization of prices." Yavlinsky is the principal author of the aborted 500-day radical reform plan offered last year and coauthor, along with a Harvard University team, of the "Grand Bargain" plan for Western cooperation and radical reform. One of the more difficult issues is the question of a single currency. The Baltic states have already expressed their intention to issue their own currencies, as has the Ukraine. Deputy head of the economic management committee, Arkady Volsky, told the Economic Forum meeting that he "would insist on a common currency" for the new union. But Yavlinsky indicated his draft treaty will allow every republic to have its own currency. Republican currencies don't make economic sense, reform economist Nikolai Petrakov, a former adviser to Gorbachev, told the trade union daily Trud last week. "It is a step backward, but the reality is such that disintegration of the former Soviet Union is inevitable. That is why it is necessary to at least preserve the single economic space, to separate and then unite on a new basis." If separate currencies are introduced, Mr. Petrakov suggests it will be necessary to reach an agreement on a common monetary policy and interaction of banking systems, with the value of the ruble floating freely in relation to the republican currencies. The banking system is likely to be modeled on the United States Federal Reserve system, in which all 50 states have representation. According to various reports, the treaty also includes an agreement on division of the Soviet foreign debt, and it reserves funds of hard currency, gold, and diamonds. Thomas Alibegov, deputy head of the Soviet Foreign Economic Bank, told the independent Interfax news agency that the Soviet foreign debt, estimated at $60 billion to $65 billion, would be distributed among the republics. A Latvian official told a press conference on Sept. 5 that the republican officials had agreed on criteria for this division. Latvia's share of both the debt and the reserves, for example, was calculated at 0.9 percent.