Japan could have retaliatory tariffs on U.S. imports in place by the end of the year unless Washington withdraws its hefty steel tariffs, a senior official of the Ministry of Economy, Trade and Industry said Thursday.

"We will take steps calmly if the current situation does not change," vice METI chief Seiji Murata told a news conference, referring to the possibility that Tokyo will slap additional tariffs on some U.S. products in retaliation for the "safeguard" steel import restrictions.

But in practice it may be difficult for Japan to do so, considering such retaliatory tariffs would require that government ordinances be amended just ahead of the yearend holidays, Murata said.