Soviet officials say the immense cost of raising new cities from the rubble of the Armenian earthquake will slow Mikhail S. Gorbachev's efforts to achieve social and economic reforms.

Deputy Prime Minister Yuri Bata-lin told reporters in the Armenian capital of Yerevan on Monday that housing construction will begin next month in the cities and villages destroyed in the Dec. 7 quake, Tass reported.The new buildings will be significantly more resistant to seismic activity than those that collapsed in the quake, the official news agency quoted him as saying.

The quake, which measured 6.9 on the Richter scale, leveled the cities of Leninakan, Kirovakan and Spitak, as well as up to 100 villages, and left more than 500,000 people homeless.

Prime Minister Nikolai I. Ryzh-kov, who heads a Politburo commission overseeing relief efforts, was quoted by Tass as saying reconstruction will cost much more than the $8.3 billion originally estimated.

He called the destruction "enormous" and said the disaster and relief effort dealt a palpable blow to the national economy and Gorbachev's campaign for change, Tass reported.

The cost of rebuilding "will affect the implementation of the social programs being carried out in the course of economic reform in the USSR," Ryzhkov said.

Leninakan and Kirovakan will be rebuilt on the same sites, while Spitak will be shifted to a spot where there is less danger of another earthquake, according to Ryzhkov. New buildings will not exceed three to four stories.

Almost every building of more than five stories collapsed in the quake, and officials all the way up to Gorbachev have criticized shoddy construction they say contributed to a death toll in the tens of thousands.

The Communist Party daily Pravda estimated Monday that 40,000-45,000 people were killed in the quake, at least 10,000 fewer than an earlier toll of 55,000 given by Soviet officials.

Ryzhkov announced that a government commission was formed to investigate technical violations in the construction of high-rise apartments and other buildings in "an area of seismic danger."