The Soviet Union broke its silence tonight on the seven-week-long labor unrest in Poland by underscoring Polish leader Edward Gierek's warning that Poland can "only be an independent country under socialism."

A summary of Gierek's speech was distributed here by the news agency Tass 24 hours after he delivered it over Polish radio and television last night. It suggested growing Soviet concern over what has developed into a political challenge to the communist government of Moscow's largest East European ally.

Tass referred to the Polish strikes as "work stoppages" and provided no details about the extent of labor troubles or the issues involved.

It quoted Gierek as saying that some "irresponsible, anarchist and antisocialist elements" at unspecified enterprises on "the Gdansk coast" were attempting to use the stoppages for "hostile political aims."

The tone of the summary reflected Moscow's attitude toward the Polish situation although Tass provided no comments.

"We deem it our duty to declare most resolutely that any action directed against political and public order cannot and will not be tolerated in Poland," Tass quoted Gierek as saying. "On this issue of principles nobody can relay concessions, compromises or even hesitations.

"The socialist system is inseparably linked to Poland's state interests. Only as a socialist country can Poland be free and independent."

The agency also quoted Gierek as saying that Poland's economic problems were caused by "errors in the economic policy" and other "objective factors." It said economic losses were sustained because of "excessive consumption of energy fuel and materials, unsatisfactory discipline, low quality of production and other negative phenomena."

Observers here said the Soviets sought to stiffen Gierek's position toward the striking workers by emphasizing his tough stand outlined last night.

The first mention of the Polish unrest was also geared for the domestic audience. The Soviets were reported earlier this year to have experienced some labor difficulties in two main automobile plants.