WASHINGTON, Dec. 19 -- Donald Trump's decision to impose a partial blockade on Venezuela marks a dramatic escalation in US pressure on Venezuelan President Nicolas Maduro, but it also risks undermining a top US policy goal: deterring a potential Chinese naval encirclement of Taiwan.

The US president yesterday ordered the "total and complete blockade" of all sanctioned oil tankers entering and leaving Venezuela, a move aimed at choking the Maduro government's main source of income.

But the action immediately raised questions under international law about whether it amounts to an act of war.

In the Indo-Pacific, military planners have long feared that China might use a naval blockade to coerce democratically governed Taiwan to accept Bei...