Japan will probably be able to avoid the worst effects of U.S. President Donald Trump's sudden decision to raise tariffs on metal imports, but the move has rattled the U.S. ally and would hurt its economy if it leads to a broader trade war.

Implementation of the tariffs is slated for Friday. Australia has secured an exemption but so far Japan has been left out in the cold. If the duties are fully imposed on domestic steel and aluminum exports, the direct effect may still be limited as the country is not a big exporter to the U.S.

But the proposal from Japan's closest ally and second-largest trading partner comes at a bad time for Prime Minister Shinzo Abe, who is weakened by plummeting support over a cronyism scandal and was also kept out of the loop over a planned meeting between Trump and North Korea's Kim Jong Un. The larger concern is that the tariffs may lead to retaliation from other countries, and damage global trade and the domestic economy.