ZURICH (Reuters) - Swiss steelmaker Schmolz+Bickenbach STLN.S has lost a $420 million contract to supply the U.S. Air Force with warhead bodies used in bunker-busting bombs and is considering an appeal, it said on Friday.

The company confirmed a Bloomberg report that its U.S. unit lost the five-year deal because its foreign ownership drew complaints from rivals, although it noted that was already the case when it won the contract this year.

The company was reviewing whether to take legal action in response, a spokeswoman said.

The U.S. decision had nothing to do with major shareholder Viktor Vekselberg, she added. The Russian businessman faces U.S. sanctions over allegations of Russian meddling in U.S. elections, which Moscow denies.

The contract would have generated most revenue from 2020, so the impact on this year would be limited. Schmolz+Bickenbach generated first-half sales of 1.74 billion euros ($2.03 billion).

Its shares fell 4.5 percent by 0930 GMT.