The Soviet Union, in an unexpectedly sharp attack, accused China today of raising claims to more than 577,000 square miles of Soviet territory in an effort to "retard the process of normalization" of relations.

The attack came in an article published by the journal New Times and distributed in advance by the government news agency Tass. It was surprising because it followed several months of conciliatory gestures by both sides including the resumption of political talks aimed at improving relations.

China's "claims" to the vast area--more than twice the size of Texas--include the city of Vladivostok, Lake Baikal and much of Kazakhstan, the article said.

"Claims are being advanced more and more persistently to Soviet territories alleged to have belonged to China at one time and 'justification' is sought for these pretensions," the article said.

The Chinese are also declaring as "unequal" the treaties on which the precise demarcation of some sections of the Sino-Soviet border is based, it said.

Today's article, signed by "Observer," clearly was by a senior official bearing the Kremlin leadership's approval. It was the first public attack here on Peking in more than six months. Since last February, the Soviets have been assiduously wooing China in an effort to normalize relations burdened by nearly 20 years of quarreling over ideology, frontiers and other issues.

The two Communist giants finally resumed political negotiations in Peking last October, and a second round of these talks was expected to reopen in Moscow in March.

A Chinese spokesman formally announced Friday that the talks will take place in Moscow early in March, Agence France-Presse reported.

One indicator of an improvement in Sino-Soviet relations is their bilateral trade, which jumped from a total of $330 million in 1981 to $880 million in 1982. The article carried by Tass declared:

"On the whole, the impression is that the Chinese side is keeping the border issue as a ready-made sure expedient for retarding the process of normalization. To this end the border settlement is replaced by territorial claims on the Soviet Union.

"A genuine striving to improve and normalize Soviet-Chinese relations presupposes clear and unconditional renunciation of territorial claims on each other--however these are expressed."

Tass quoted the article as saying that Chinese claims have nothing in common "with the historical truth," that the history of the demarcation of the border was "a long and complex one" but that "the fact remains that Russia never seized any Chinese territory." It said "the territories which Peking qualifies as so-called Chinese lands" were "actually never part of the Chinese state nor was their population Chinese."

It said that "some pronouncements" by Chinese leaders and by "current Chinese propaganda releases" contradict Peking's stated readiness to improve Sino-Soviet relations. It said "attempts are being made to provide scientific substantiation" for various contentions.

The article said the Chinese describe as "former" Chinese territory "seized by imperialist Russia" lands that also include the city of Khabarovsk in the Far East, the island of Sakhalin, the Ussuri and Amur River basins, large territories of Soviet Kirkhizia and Kazakhstan, the eastern maritime territory, Lake Balkhash and the whole of the Pamir highlands in Central Asia.

In quoted two Chinese publications, Shehuei Kexue Zhanxian and Xuexi Yu Tansu, as printing "in practically every issue" articles that misrepresent history.

"Even wider currency is being given to maps of the so-called historical territories which, it is claimed, once belonged to China and were 'seized' by Russia," the article said, adding that such maps "invariably" are included in textbooks used in schools and universities.

"All this can hardly be qualified as anything other than a form of presenting territorial claims on the Soviet Union," the article said.

It said the purpose of such publications is "to bring up the new generation in a spirit of distrust and enmity toward a neighboring country."