Jan 19 (Reuters) - Investors headed for safe havens while Europe prepared to push back on Monday after U.S President Donald Trump threatened escalating tariffs on allies in the way of his ambition to buy ​the Danish arctic territory of Greenland. Trump said additional 10% tariffs would take effect on February 1 on goods ‌from Denmark, Norway, Sweden, France, Germany, the Netherlands, Finland and Great Britain, rising to 25% on June 1 unless some sort of Greenland deal is ‌struck. Precious metals and bon ...