The U.S. administration of President Donald Trump has taken a hard line on Japan's possible participation in U.N. talks later this month on a treaty to outlaw nuclear weapons, sources close to bilateral ties said Wednesday.

In conveying its opposition, Washington has used an expression indicating its strong aversion, the sources said. Japan has not made clear whether it will join the talks starting March 27 at the U.N. headquarters in New York.

While advocating a world free of nuclear weapons as the only country ever attacked with atomic bombs, Japan also relies on U.S. nuclear deterrence for protection.