The annual meeting of the world's political and business elite at the luxury Swiss ski resort often draws small protests against its famous participants and the global trade agenda.
But with the surprise announcement this week that Trump is attending this year's January 22-26 meet, Swiss authorities expect demonstrations across the country.
"In connection with the upcoming WEF in Davos and the announced visit of US President Donald Trump, an unauthorised demonstration was called" on January 13, Bern said, warning that "a high potential for violence must be assumed."
A group called RJG has called a demonstration in the Swiss capital starting at 3:00 pm (1400 GMT) Saturday, but authorities said they expected protests could begin on Friday evening.
Authorities expect "several hundred demonstrators" to turn up, the statement said, adding that "damage to federal objects must be expected."
"It cannot be ruled out that demonstrations will be called again for the following weekend," it said.
'Welcome to Hell'
It remains unclear when Trump will be at Davos, but RJG has called a demonstration on January 23 titled: "Trump: Welcome to Hell" in Zurich, a 2.5-hour drive or train ride from Davos and the closest airport.
Another group, Campax, which has gathered more than 8,100 signatures since Wednesday on a petition aimed at keeping Trump away from Davos, has also vowed to organise a demonstration near the Zurich airport around the time of his arrival.
A previously planned rally in Geneva on January 21 to mark the anniversary of the massive Women's March in Washington and around the world after Trump was sworn in is also now expected to draw a far bigger crowd, Le Temps daily reported.
Trump, whose "America First" agenda stands in stark contrast with the globalisation and regulatory integration popular among the Davos crowd, will be the first sitting US president to attend the meeting since Bill Clinton in 2000.
Ensuring security during WEF requires a massive police and military presence but Swiss authorities did not appear too rattled.
The head of the regional Graubunden police force Walter Schlegel told Swiss news agency ATS that Trump's attendance would not require "major shifts" in the security detail in the resort town of around 11,000 inhabitants.
The airspace over the region will remain closed for the duration of the forum, and like every year, the military will pitch in by sending up to 5,000 troops to Davos.
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