FILE PHOTO: The logo of Swiss drugmaker Roche is seen at its headquarters in Basel, Switzerland February 1, 2018. REUTERS/Arnd Wiegmann/File Photo

By Paul Arnold

ZURICH (Reuters) -Swiss companies Roche and Novartis on Friday flagged they did not expect to be hit by President Donald Trump's latest pharmaceutical tariff announcement because they are in the process of building new U.S. sites and investing there.

Trump said on Thursday the United States will impose a 100% tariff on imports of branded or patented pharmaceutical products from October 1, unless a given pharmaceutical company is building a manufacturing plant in the U.S.

A Roche spokesperson pointed to an August 25 announcement that its Genentech unit had broken ground for a facility in Holly Springs, North Carolina, as well as its $50 billion pledge to invest in U.S. manufacturing and research and development.

Roche and Novartis are Switzerland's two biggest pharmaceutical firms with major U.S. production operations.

Novartis, which made a $23 billion U.S. investment pledge earlier this year, said that Trump's 100% tariff announcement should not have an impact on the company.

"We have ongoing construction and expect to announce five new sites to be under construction before end of year," Novartis said.

Investors appeared to shrug off the news. Shares in both Roche and Novartis traded slightly up early on Friday.

Wolf von Rotberg, an equity strategist at J. Safra Sarasin Sustainable Asset Management, advised against significantly reducing pharmaceutical investment after Trump's announcement.

"If exemptions apply broadly to companies with U.S. production sites, all major U.S. pharmaceutical companies and some European ones would likely be exempt," he said.

"Recent spending commitments by large-cap pharmaceutical companies, including major Swiss firms, may be deemed sufficient for exemptions, potentially limiting the tariff's scope", he added.

The Swiss government said the relevant departments are analysing the potential impact of Trump's pharmaceutical tariff measures but that it did not have details of them.

(Reporting by Paul Arnold and Dave Graham, editing by Friederike Heine and Thomas Seythal)