U.S. President Donald Trump has pinned much of the blame for Washington's planned exit from the Intermediate-Range Nuclear Forces Treaty (INF) on Russian violations of the landmark pact. But a closer look shows that China's buildup of its missile forces — which pose a grave threat to U.S. military bases in Japan and elsewhere in the region — may also play a large part in any decision to abrogate the 31-year-old arms-control deal.

Trump on Sunday said the U.S. would scrap the 1987 treaty between Washington and Moscow, which bans all land-based missiles with ranges of 500 to 5,500 km (310 to 3,420 miles). The pact covers missiles, known as short- and intermediate-range, that can carry both nuclear and conventional warheads, but does not ban air- or sea-launched weapons.

The historic bilateral pact, however, has left China unconstrained to amass a missile arsenal that puts U.S. and Japanese forces at risk, according to observers.