MOSCOW (AP) _ A West German teen-ager who flew unimpeded through hundreds of miles of Soviet airspace and landed his plane in Red Square will be put on trial here, a West German Embassy official said today.

The Embassy has not yet been told when 19-year-old Mathias Rust will be tried or what charges he will face, embassy legal counselor Gerhard Enver Schroembgens told The Associated Press. But Schroembgens said he expected to learn those details from Soviet officials next week.

In the Soviet Union, violation of international flight regulations carries a penalty of up to 10 years in jail or a fine of $1,550. Illegal entry into the country carries a sentence of up to three years.

''We were informed that he (Rust) has been given a Soviet lawyer and the Embassy has asked to be present at the trial,'' Schroembgens said. ''I plan to visit him on Tuesday.''

On May 28, Rust flew a borrowed single-engine Cessna from Finland through 500 miles of some of the most tightly controlled airspace in the world, buzzed the Kremlin walls and landed in Red Square.

Rust's parents have described their son as an idealist who apparently flew to Moscow in an effort to promote understanding between East and West.

But a Tass news agency dispatch soon afterward accused Rust of violating Soviet airspace. In the wake of the flight, Kremlin authorities fired Air Marshal Alexander Koldunov and accepted the resignation of Defense Minister Sergei Sokolov.

Rust has been in custody since landing in Moscow, but the West German government has been allowed periodic meetings with him, and his parents visited him last month.

Schroembgens, who last saw Rust two weeks ago at Lefortovo Prison in eastern Moscow, described the teen-ager's mood then as good.