BUCHAREST, DEC. 14 -- Communist leader Nicolae Ceausescu called today for further belt-tightening for hard-pressed Romanians, who last month staged unprecedented public protests over severe shortages of food and energy.

Opening a Communist Party conference, Ceausescu rejected economic reforms and said workers in the Soviet Bloc nation must raise productivity. In a four-hour speech to 5,000 party delegates, Ceausescu said Romania has failed to reach some of its economic targets. He pledged some pay increases and said 1988 will be "a decisive year."

But the party leader, 69, ruled out economic reform of the type promoted by Soviet leader Mikhail Gorbachev and instead strongly defended his central planning.

Market forces have little role to play in a communist society, Ceausescu said: "It is hard to understand how solving the problems of economic development can be left to the vagaries of supply and demand, how projects can be assured by so-called market socialism."

Ceausescu's speech made clear that Romania will remain the Soviet Union's only East European ally to reject economic and social reforms.

Romanians are entering their fourth straight winter of harsh energy saving decrees. This year both electricity and gas are rationed even more than last year.

Food has been rationed since the early 1980s, and milk and meat are almost impossible to obtain for the average family.

Despite the rationing, Ceausescu complained that Romanians have failed to reduce consumption enough over the past year. "We must better save our raw materials and reduce our consumption of power," Ceausescu told delegates.

Ceausescu made clear he wants to maintain high investment in key industries earning hard currency through exports. This includes the petrochemical, oil refining and machine building sectors.

Bucharest-based western diplomats say reported protests by Romnanian activists are a sign of mounting dissatisfaction.

At least 10,000 workers took part in a demonstration on Nov. 15 in Brassov in central Romania, demanding more food and better heating and shouting anti-Communist slogans.

Romanian officials have denied that any protests took place, but acknowledged that some workers in Brasov were briefly "angered by the incompetence" of the factory managers.

In a move apparently intended to placate restless workers, Ceausescu announced an increase in wages, to be implemented gradually starting in 1988.