China said Tuesday that it “will not stand idly by” and will take countermeasures if the US deploys intermediate-range missiles in the Asia-Pacific region, which Washington has said it plans to do within months. Such weapons are undercutting regional deterrence at the same time as China is boosting its ability to strike the continental US with intercontinental ballistic missiles and hypersonic glide weapons, said Collin Koh, a regional security expert at NTU Singapore.