A trade deal reached by Japan and the United States after months of talks has turned out to be exceedingly fragile, as it emerged that the two countries view the handshake agreement very differently.

The lack of formal documentation and slow implementation by the United States of a key tariff concession have left open the possibility that there's not much of deal to begin with.

“The recent Japan-U.S. agreement regarding U.S. tariff measures does not constitute a legally binding international commitment,” economy and fiscal policy minister Ryosei Akazawa told a Lower House budget committee hearing on Monday.