Swiss companies have already invested USD 27 bn in the American economy this year.
The investments are meant to keep US import tariffs on Swiss goods at 10%, after they were threatened with rising to 39%.
Novartis, Roche and shipping group MSC are among the firms expanding US production and headquarters.
But Washington has now added a 2.5% surcharge on countries it accuses of weak action against forced labour, a list that includes Switzerland.
Bern disputes the claim and is pushing for a renegotiated trade deal to head off further escalation.
Ski resorts popular this summer
Heatwaves force construction rethink
Customs warn of bringing back fake goods
Swiss firefighters replaced in France
Cities remain dangerous for cyclists
Govt looks to cut forest protection
