Having toppled Mr. Slobodan Milosevic, Yugoslavia's new president, Mr. Vojislav Kostunica, must now consolidate power if he is to return his country to the family of European nations. His efforts to form an interim government have been hampered by Yugoslavia's federal structure and the bad blood between its two constituent parts, Serbia and Montenegro. Mr. Milosevic's Socialist People's Party, which has not given up hope of returning to power, is doing its best to complicate matters for the new president. The West can help, but it must tread carefully: The Serb people harbor deep resentments after the NATO bombings during the Kosovo War.

As difficult as it was to get Mr. Milosevic to respect the will of the Yugoslav people, forcing politicians and bureaucrats to do the same may prove equally challenging. Every level of the government administration is still in the hands of supporters of the ousted president. Mr. Kostunica's democratic alliance is the largest bloc in the 178-seat federal Parliament, but it does not hold a majority.

Last week, the president struck a deal with the Socialists that will allow him to establish an interim government until parliamentary elections are held in December. Under the agreement, power will be shared among Mr. Kostunica's political allies and the Socialists. The Socialists will hold the post of prime minister, but he must reach a consensus with two deputy prime ministers from the democratic parties. The Socialists, the Democratic Opposition of Serbia and the Serbian Renewal Movement will jointly control key ministries, including the Interior Ministry which commands a police force of 85,000.