LONDON - U.S. President Donald Trump’s threat to slap new tariffs on trade partners the U.S. accuses of failing to crack down on forced labor will do little to fight modern slavery — and could even make things worse, experts, business groups and some human rights groups say.In its latest trade salvo, the Trump administration proposed additional duties of 10% or 12.5% on imports from ​60 countries for failing to curb trade in goods made with forced labor, an assertion that U.S. trading partners rejected.The plan from ‌the U.S. ‌Trade Representative’s office comes from a Section 301 unfair trade practices investigation designed to help restore Trump’s emergency ​tariffs, struck down by the U.S. Supreme Court in February.