Indeed, we are. PRC Deputy Director of Foreign Ministry Information Department Hua Chunying said

We are severely concerned about relevant remarks made by the American side. We believe the American side needs to make clarification on that[.]

That’s in response to SecDef Ash Carter’s remarks that he’d asked his folks to look into potential responses to the PRC’s seizure and occupation of the South and East China Seas. In particular, those responses might

include flying Navy surveillance aircraft over islands and sending US Navy ships within 12 nautical miles of reefs that have been built up in recent months around the Spratly Islands.

We should be severely concerned. Those surveillance aircraft should be accompanied by fighter aircraft, and they should buzz the construction sites. And keeping the Navy a dozen miles away, instead of sailing up close and personal, seems awfully timorous to me.

Those islands, after all, are in international waters, and they’re in the Exclusive Economic Zones of Vietnam, Malaysia, and the Philippines—who have shown a willingness to resolve their dispute without military occupation. Thus, their aircraft and naval ships should be accompanying ours on those close approaches.

Our own action alone, though, would be a good start on a proper response to the PRC’s aggression.

Also creating severe concern—or should be—is this bit:

Privately, many diplomats and leaders in the region say they worry about the potentially destabilizing impact of a confrontation between Washington and Beijing.

No, guys, what would be destabilizing would be letting that PRC aggression go unchallenged.