Sentence:  Even so, the current crisis might well have been defused weeks ago, before the two leaders started exchanging threats of war, had the United States agreed to talk directly to North Korea, as our allies in the region have been pleading with us to do. Instead, the Administration <WSD>drew a line in the sand</WSD>, insisting that the United States would not be blackmailed into one-on-one talks with North Korea. 
Meaning of the word marked with <WSD> tags:  To indicate the threshold or level above which something will become unacceptable or will provoke a response; to create a boundary and imply or declare that its crossing will provoke a (negative) response.