If the united states threatens to use military force to keep shipping lanes open near the spratly islands in the south china sea despite chinese claims that the islands are part of their territory, which strategy is the united states using?

Deterrence is the correct answer.

In a broader term, deterrence is the art of convincing someone not to do something. In International Relations, deterrence is a military strategy used by leaders of one country to leaders of the other country. It prevents military attacks from taking place by using the threat of reprisal in an effective manner.  

answer; through play and social interaction;