Cryptocurrency campaigners have stepped up calls for the Swiss National Bank to buy bitcoin, saying the global economic turmoil triggered by U.S. President Donald Trump 's tariffs made it more important for the central bank to diversify its reserves.Supporters launched a referendum campaign in December to change the Swiss constitution to require the SNB holds bitcoin in its reserves alongside gold."Holding bitcoin makes more sense as the world shifts towards a multipolar order, where the dollar and the euro are weakening," said campaigner Luzius Meisser, a board member of cryptocurrency broker Bitcoin Suisse.