BELGRADE, Yugoslavia (AP) _ President Raif Dizdarevic told government officials today that nationwide unrest threatens political stability, and he urged quick economic reform, an official report said.

''Political and ethnic tensions have increased to such a degree that the political security situation has seriously deteriorated,'' Dizdarevic told an emergency session of the collective presidency he leads and its Cabinet.

The collective presidency has nine members who represent regions across the nation. Its rotating annual president functions as chief of state.

Economic and social problems have combined to prompt months of anti- governmen t demonstrations with calls for an overhaul of Communist Party leadership and introduction of a multiparty system.

''The perspective of the exit from the economic crisis can not be put off any longer,'' Dizdarevic was quoted as saying by Tanjug, the official news agency. ''It is the final hour (in which) we direct and concentrate all forces for final preparation of the economic reform.''

Communist leaders have faced hundreds of strikes in recent months after eight years of economic crisis that have eroded the standard of living. Annual inflation stands at 217 percent, and employment is 15 percent.

At the same time, Serbian nationalist demonstrations have heightened friction between Serbs and other groups in this fragile confederation of republics.

Only two emergency meetings of government leaders, both dedicated to economic problems, have been held since World War II, in 1981 and 1985.

Dizdarevic also appealed to the Soviet Union to help Yugoslavia cope with its $1.7 billion deficit in trade with Moscow.

The party's policy-making Central Committee held a session earlier this month and pledged radical economic reforms, including introduction of a market-oriented economy and stimulation of private entreprise. The changes are expected to be adopted by Parliament by the end of the year.