WASHINGTON — America’s diplomatic and defense chiefs sought Thursday to reinforce the threat of possible U.S. military action against North Korea after President Donald Trump’s top strategist essentially called the commander-in-chief’s warnings a bluff.

Secretary of State Rex Tillerson stressed after security talks with close ally Japan that the U.S. seeks a peaceful solution to the standoff over North Korea’s nuclear weapons program. But he said a U.S.-led campaign of economic pressure and diplomacy needs to be backed by potential military consequences.

Washington is “prepared militarily” to respond, if necessary, he said.