Almost lost in the din of the upcoming U.S.-North Korea summit and fresh tension between Washington and Beijing last week, India cemented its diplomatic and security ties across Southeast Asia in a clear challenge to China.

It is not clear just how far New Delhi will take these relationships, given years of promise, and a general election due in 11 months that could be a distraction for Prime Minister Narendra Modi. And if India is already rattling China, it won't want to spark open confrontation.

But Modi took several concrete foreign policy and security steps in Southeast Asia in recent days.