The Soviet Union has invited the International Labor Organization (ILO) to send a mission to examine living and working conditions on the Trans-Siberian pipeline, a spokesman for the 158-nation U.N. agency said today.

The invitation, issued Oct. 25 by the Soviet Central Council of Trade Unions, was in apparent response to recent charges by the State Department and by the International Confederation of Free Trade Unions (ICFTU) that forced labor is being used on the natural gas pipeline project, although no mention of the charges was made in the text of the invitation.

ILO press officer Kyril Tidmarsh said today the Soviet authorities had invited the U.N. agency to send one high official, accompanied by two others, to enter into "a dialogue" on living and working conditions on the pipeline sites.

Charges that the Soviets are using forced labor on the controversial pipeline project first surfaced in August, when the ICFTU, a social democratic labor group based in Brussels, wrote to ILO Director General Francis Blanchard to suggest that labor conditions on the pipeline are in violation of ILO conventions banning forced labor. The complaint followed charges by the West German-based International Society for Human Rights that 100,000 slave laborers were working on the pipeline.

The Soviet Union has ratified an early basic ILO convention on forced labor but not a later one specifically outlawing the use of political prisoners on labor projects.

Last weekend the State Department cited a study by the Central Intelligence Agency that found it "unlikely" that there is now large-scale use of forced labor on the pipeline because many of the jobs require special skills. The study also said, however, that penal workers had been used on unskilled aspects of pipeline construction, such as ground clearing in the Ukraine, Kazakhstan and the central Russian Republic.

The CIA study said the Soviet Union has about 4 million forced labor workers, of whom about 10,000 are political prisoners. In recent months, there have also been reports, including in the West German press, that part of the pipeline labor force is made up of Vietnamese workers, a portion of whose wages is withheld to help pay Hanoi's debts to its Soviet ally.